SECTION PAGE
8.0 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 18.1 DIVE PLANNING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 1
8.1.1 Selection of Diving Equipment . . . . . . . . . . . . . . . . . . . . . . 8- 28.2 DIVE TEAM ORGANIZATION . . . . . . . . . . . . . . . . . . . . . . . . 8- 2
8.2.1 Divemaster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 28.2.2 Diving Medical Officer/
Diving Medical Technician . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.2.3 Science Coordinator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.2.4 Divers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.2.5 Support Divers and Other
Support Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.3 ENVIRONMENTAL CONDITIONS . . . . . . . . . . . . . . . . . . . . . 8- 3
8.3.1 Surface Environmental Conditions . . . . . . . . . . . . . . . . . . . 8- 38.3.2 Underwater Environmental
Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 48.4 DIVING SIGNALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 8
8.4.1 Hand Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 88.4.2 Surface-to-Diver Recall Signals . . . . . . . . . . . . . . . . . . . . . 8-118.4.3 Line Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-118.4.4 Surface Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11
8.5 AIR CONSUMPTION RATES . . . . . . . . . . . . . . . . . . . . . . . . . . 8-118.5.1 Determining Individual Air
Utilization Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-148.5.2 Scuba Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-148.5.3 Scuba Air Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-168.5.4 Surface-Supplied Air Requirements. . . . . . . . . . . . . . . . . . . 8-17
8DivePlanning
8.0 GENERALDiving with air as the breathing gas is conducted
using a variety of life-support equipment. The most fre-quently used mode is open-circuit scuba, where the divercarries the compressed air supply. Divers can also useumbilical-supplied air with a scuba regulator, and either afull-face mask or a lightweight diving helmet. This sectiondeals with planning for air dives, operational methods ofcalculating air supply requirements, personnel require-ments, and environmental conditions.
8.1 DIVE PLANNINGCareful and thorough planning are the keys to con-
ducting an efficient diving operation and are imperativefor diver safety as well. The nature of each dive operationdetermines the scope of the planning required. The diveplan should take into account the ability of the least quali-fied diver on the team and be flexible enough to allow fordelays and unforeseen problems. It should include at leastthe following:
• Definition of Objectives– A clear statement of the purpose and goals of the
operation• Analysis of Pertinent Data
– Surface conditions, such as sea state, air tempera-ture, and wind chill factor
– Underwater conditions, including water tempera-ture, depth, type of bottom, tides and currents,visibility, extent of pollution, and hazards
– Assistance and emergency information, includinglocation, status, and contact procedures for thenearest recompression chamber, air evacuationteam, U.S. Coast Guard, and nearest hospital
• Diving Team Selection– Divemaster– Medical personnel– Tenders/timekeeper – Coxswain/surface-support personnel
• Diving Mode Selection– Skin (snorkeling)
– Open-circuit scuba– Rebreathers– Surface-supplied– Hookah
• Equipment and Supplies Selection– Breathing gas, including a backup supply– Dive platform and support equipment, including
diver/crew shelter – Oxygen resuscitator and first aid kit– Backboard– Dive flag – Diving gear, tools, etc.– Water– Communications
• Schedule of Operational Tasks for All Phases– Transit to the site– Assembling dive gear and support equipment– Predive briefing– Calculating allowable/required bottom time– Recovery– Cleaning, inspection, repair, and storage of gear – Debriefing of divers and support personnel
• Final Preparations and Safety Checks– Review of dive plan, its effect, and all safety pre-
cautions– Outline diving assignments and sequence– Complete and post on-site emergency checklist– Review diver qualifications and conditions – Secure permission from command or boat captain
for dive• Briefing/Debriefing the Diving Team
– The objective and scope of the operation– Conditions in the operating area– Diving techniques and equipment to be used– Personnel assignments– Specific assignments for each diver– Anticipated hazards– Normal safety precautions– Any special considerations – Group discussion period to answer questions by
members of the diving team
8-1
8Dive Planning
8.1.1 Selection of Diving EquipmentThe selection of the proper diving equipment
depends on environmental conditions, qualifications ofdiving personnel, objectives of the operation, and divingprocedures to be used. Although most diving is per-formed at depths less than 130 ft. (39.6 m) and oftenuses open-circuit scuba, some missions can be accom-plished using only skin diving equipment. Other morecomplex assignments require surface-supplied or closed-circuit systems. Depth and duration of the dive, ques-tions about the type of work to be accomplished (heavywork, light work, silent work), temperature of thewater, velocity and nature of current, visibility, logis-tics, and the diver’s experience and capabilities all influ-ence the selection of diving equipment. Detaileddescriptions of the various types of diving equipmentare presented in Chapter 5. For planning purposes, thefollowing guidelines may be used in selecting the appro-priate diving equipment.
Breath-Hold Diving Equipment
Generally Used For:• Scientific observation and specimen collection in
shallow water in areas where more complex equip-ment is a disadvantage or is not available
• Shallow-water photography• Scouting for diving sites
Major Advantages:• Less physical work required to cover large surface
areas• Simplified logistics• Fewer medical/physiological complications
Major Disadvantages:• Extremely limited in depth and duration• Requires diver to develop breath-holding tech-
niques• Can only be used in good sea conditions
Open-Circuit Scuba
Generally Used For:• Scientific observation• Light underwater work and recovery• Sample collection• Shallow-water research• Ship inspection and light repair
Major Advantages:• Minimum support requirements• Mobility• Accessibility and economy of equipment and
breathing medium• Portability• Reliability
Major Disadvantages:• Lack of efficient voice communication• Limited depth and duration
Umbilical-Supplied Systems
Generally Used For:• Scientific investigation• Ship repair and inspection• Salvage• Long-duration scientific observation and data
gathering• Harsh environments (low visibility, strong currents,
polluted water)Major Advantages:
• Long duration• Voice communication• Protection of diver from environment
Major Disadvantages:• Limited mobility• Significant support requirements
Closed-Circuit Systems
Generally Used For:• Observations of long duration
Major Advantages:• Mixed-gas capability• No noise or bubbles• Conservation of breathing medium• Long duration
Major Disadvantages:• Complicated maintenance• Extensive training requirements• Cost of equipment
8.2 DIVE TEAM ORGANIZATION8.2.1 Divemaster
NOAA Divemasters have complete responsibility for thesafe and efficient conduct of all NOAA diving operations. Inorder to be a NOAA Divemaster, individuals must be certi-fied NOAA Working Divers, or higher, and have completedthe NOAA Divemaster training program. When no divemas-ter is present, diving should not be conducted. The divemas-ter’s responsibilities include, but are not limited to:
• Overall responsibility for the diving operation• Safe execution of all diving• Preparation of a basic plan of operation, including
evacuation and accident management plans• Liaison with other organizations• Inspection of equipment• Proper maintenance, repair, and stowage of equip-
ment• Selection, evaluation, and briefing of divers and
other personnel• Monitoring progress of the operation, and updating
requirements as necessary• Maintaining the diving log• Monitoring of decompression (when required)• Coordination of boat operations when divers are in
the water
8-2 NOAA Diving Manual
The divemaster is responsible for assigning all divers toan operation and for ensuring that their qualifications areadequate for the requirements of the dive. The divemastermust ensure that all divers are briefed thoroughly about themission and goals of the operation. Individual responsibili-ties are assigned to each diver by the divemaster. Where spe-cial tools or techniques are to be used, the divemaster mustensure that each diver is familiar with their application.
Training and proficiency dives should be made toensure safe and efficient operations. During complex opera-tions or those involving a large number of divers, divemas-ters should perform no diving, but should, instead, devotetheir efforts entirely to directing the operation.
The divemaster is in charge when divers are in thewater during diving operations. Before any change is madeto the boat’s propulsion system (e.g., change in speed,direction, etc.), the boat captain must consult with thedivemaster.
8.2.2 Diving Medical Officer/Diving Medical Technician
When it is not practical to have a qualified diving med-ical officer on site, a Diving Medical Technician trained inthe care of diving casualties shall be assigned. The DMT istrained to respond to emergency medical situations and tocommunicate effectively with a physician not at the divingsite. There are specialized courses available to train DivingMedical Technicians in the care of diving casualties.
In the event that neither a physician nor a trained tech-nician is available, the divemaster should have available thenames and phone numbers of at least three diving medicalspecialists who can be reached for advice in an emergency.Emergency consultation is available from the service centerslisted below. Referred to as a “Bends Watch,” each of theseservices is available to provide advice on the treatment ofdiving casualties:
• Divers Alert Network, Peter B. Bennett Center, 6West Colony Place, Durham, North Carolina 27705,telephone (919) 684-8111 (ask for the DivingAccident Physician)
• Navy Experimental Diving Unit, Panama City,Florida 32407, telephone (850) 234 -4351
• Brooks Air Force Base, San Antonio, Texas 78235,telephone (210) 536-3278 ( before 7:00 a.m. andafter 4:15 p.m. MST), emergency call (210) 536-3281 (Monday thru Friday between 7:00 a.m. and4:15 p.m. MST)
All diving personnel shall have access to the phonenumbers of these facilities, available at all times, especially ifthey will be diving in remote areas.
8.2.3 Science CoordinatorOn missions where diving is performed in support of
scientific programs, a chief scientist may be needed.
The chief scientist is the prime point of contact for allscientific aspects of the program, including scientificequipment, its use, calibration, and maintenance.Working with the divemaster, the chief scientist willbrief divers on specific scientific tasks to be completedand supervise the debriefing and sample or data accumu-lation after a dive.
8.2.4 DiversAlthough the divemaster is responsible for the overall
diving operation, the diver is responsible for being inproper physical condition, for checking out personalequipment before the dive, and for thoroughly under-standing the purpose and the procedures to be used for thedive. The diver is also responsible for refusing to divewhen conditions are unsafe, when not in good mental orphysical condition, or when diving would violate dictatesof their training or applicable standards.
8.2.5 Support Divers and Other Support PersonnelIn most diving operations, the number and types of
support divers depend on the size of the operation and thetype of diving equipment used. Ideally, those surface-sup-port personnel working directly with the diver also shouldbe qualified divers. Using unqualified personnel who donot understand diving techniques and terminology maycause confusion and can be dangerous. Persons not quali-fied as divers can be used when the need arises, but onlyafter they have demonstrated that they understand proce-dures to the satisfaction of the divemaster.
8.3 ENVIRONMENTAL CONDITIONSEnvironmental conditions at a dive site should be con-
sidered when planning a diving operation. Environmentalconditions can be divided into surface conditions andunderwater conditions. Surface conditions include weather,sea state, and amount of ship traffic. Underwater condi-tions include depth, bottom type, currents, water tempera-tures, and visibility. Regional and special diving conditionsare discussed in Chapter 12.
8.3.1 Surface Environmental ConditionsWhen planning a dive, weather conditions are an
important factor. Whenever possible, diving operationsshould be cancelled or delayed during bad weather.Current and historical weather data should be reviewed todetermine if conditions are acceptable and are predicted tocontinue long enough to complete the mission. Continuousmarine weather broadcasts are provided by NOAA on thefollowing frequencies depending on the local area:
162.40 MHz, 162.475 MHz, or 162.55 MHz
These broadcasts can be heard in most areas of the UnitedStates and require only the purchase of a VHF radioreceiver. Weather radios are designed to receive onlyNOAA radio broadcasts. Regular weather forecasts and
Dive Planning 8-3
special marine warnings are available any time of the day ornight. Although both receivers pick up weather signals fromapproximately the same distance, the two-way systems havethe advantage of transmission quality.
In some cases, surface weather conditions may influ-ence the selection of diving equipment. For instance, eventhough water temperature may permit the use of standardwetsuits, cold air temperature and wind may dictate that adry suit (or equivalent) should be worn when diving froman open or unheated platform.
Whenever possible, avoid or limit diving in moderateseas. Sea state limitations depend to a large degree on thetype and size of the diving platform. Diving operationsmay be conducted in rougher seas from properly mooredlarger platforms such as diving barges, ocean-going ships,or fixed structures. When using self-contained equipment,divers should avoid entering the ocean in heavy seas orsurf, as well as high, short-period swell. If bad weathersets in after a diving operation has commenced, all diversshould be recalled. Except in an emergency, divers shouldnot attempt scuba or surface-supplied diving in rough seas(see Figure 8.1 and Table 8.1).
Because many diving operations are conducted inharbors, rivers, or major shipping channels, the pres-ence of ship traffic often presents serious problems. Attimes, it may be necessary to close off the area aroundthe dive site or to limit the movement of ships in thevicinity of the dive site. Ship traffic should be consid-ered during dive planning, and a local “Notice toMariners” should be issued. Anytime diving operationsare to be conducted in the vicinity of other ships, othervessels should be notified by message or signal that div-ing is taking place. Signal flags, shapes, and lights areshown in Table 8.2.
If the dive operation is to be conducted in the middleof an active fishing ground, divers must assume that peo-ple with various levels of experience and competencewill be operating small boats in the vicinity and may notbe acquainted with the meaning of diving signals.
Take the necessary precautions to ensure that theyremain clear of the area.
Surface visibility is important. Reduced visibility mayseriously hinder or force postponement of diving opera-tions. If operations are to be conducted in a known fogbank, the diving schedule should allow for probable delayscaused by low visibility. The safety of the diver and sup-port crew is the prime consideration in determiningwhether surface visibility is adequate. For example, in lowsurface visibility conditions, a surfacing scuba diver mightnot be able to find the support craft or might be in dangerof being struck by surface traffic.
8.3.2 Underwater Environmental ConditionsDive depth is a basic consideration in the selection of
personnel, equipment, and techniques. Depth should bedetermined as accurately as possible in the planning phases,and dive duration, air requirements, and decompressionschedules should be planned accordingly.
The type of bottom affects divers ability to see andwork. Mud (silt and clay) bottoms generally are the mostlimiting because the slightest movement will stir sedimentinto suspension, restricting visibility. The diver must orienthimself so that any current will carry the suspended sedi-ment away from the work area. Also, the diver shoulddevelop a mental picture of his surroundings so that his safeascent to the surface is possible even in conditions of zerovisibility.
Sand bottoms usually present little problem because vis-ibility restrictions caused by suspended sediment are lesssevere than with mud bottoms. In addition, sandy bottomsprovide firm footing.
Coral reefs are solid but contain many sharp protru-sions. Divers should wear gloves and coveralls or a wet-suit for protection if the operation requires contact withthe coral. Learn to identify and avoid corals and othermarine organisms that might inflict injury. There’s alsothe concern of not inflicting unnecessary damage to theenvironment during the process of studying it.
8-4 NOAA Diving Manual
FIGURE 8.1Sea States
SS6 Waves Start to Roll
SS5 Spindrift Forms
SS3 White Caps Form
Wav
e H
eigh
t ~ F
eet (
Avg
)
Dive Planning 8-5
TABLE 8.1Sea State Chart
Sea-General
SeaState Description
Wave HeightFeet
Wind
(Bea
ufor
t) W
ind
Forc
e
Des
crip
tion
Ran
ge (K
nots
)
Win
d Ve
loci
ty (K
nots
)
Ave
rage
Ave
rage
1/
10 H
ighe
st
Sign
ifica
nt R
ange
of
Perio
ds (S
econ
ds)
t (A
vera
ge P
erio
d)
I (Av
erag
e W
ave
Leng
th)
Min
imum
Fet
ch(N
autic
al M
iles)
Min
imum
Dur
atio
n(H
ours
)
Sea
Sea like a mirror U Calm Less 0 0 0 – – – – –than 1
Ripples with the 1 Light 1–3 2 0.05 0.10 up to 0.5 10 in. 5 18appearance of scales Airs 1.2 sec. min.are formed, but withoutfoam crests.
Small wavelets still, but 2 Light 4–6 5 0.18 0.37 0.4–2.8 1.4 6.7 ft. 8 39more pronounced; short Breeze min.crests have a glassyappearance, but do not break.
Large wavelets, crests 3 Gentle 7.10 8.5 0.6 1.2 0.8–5.0 2.4 20 9.8 1.7begin to break. Foam of Breeze 10 0.88 1.8 1.0–6.0 2.9 27 10 2.4glassy appearance. Perhaps scattered whitecaps.
Small waves, becoming 4 Moderate 11–16 12 1.4 2.8 1.0–7.0 3.4 40 18 3.8larger, fairly frequent white Breeze 13.5 1.8 3.7 1.4–7.6 3.9 52 24 4.8caps. 14 2.0 4.2 1.5–7.8 4.0 59 28 5.2
16 2.9 5.8 2.0–8.8 4.6 71 40 6.6
Moderate waves, taking a 5 Fresh 17–21 18 3.8 7.8 2.5–10.0 5.1 90 55 8.3more pronounced long Breeze 19 4.3 8.7 2.8–1.0.6 5.4 95 65 9.2form; many white caps 20 5.0 10 3.0–11.1 5.7 111 75 10are formed. (Chance ofsome spray.)
Large waves begin to form, 6 Strong 22–27 22 6.4 13 3.4–12.2 6.3 134 100 12the white foam crests are Breeze 24 7.9 16 3.7–13.5 6.8 160 130 14more extensive everywhere. 24.5 8.2 17 3.8–13.6 7.0 164 140 15(Probably some spray.) 26 9.6 20 4.0–14.5 7.4 188 180 17
Sea heaps up and white 7 Moderate 28–33 28 11 23 4.5–15.5 7.9 212 230 20foam from breaking waves Gale 30 14 28 4.7–16.7 8.6 250 280 23begins to be blown in streaks 30.5 14 29 4.8–17.0 8.7 258 290 24along the direction of the 32 16 33 5.0–17.5 9.1 285 340 27wind. (Spindrift begins to beseen.)
5
4
3
2
10
6
8-6 NOAA Diving Manual
TABLE 8.1Sea State Chart (continued)
Sea-General
SeaState Description
Wave HeightFeet
Wind
(Bea
ufor
t) W
ind
Forc
e
Des
crip
tion
Ran
ge (K
nots
)
Win
d Ve
loci
ty (K
nots
)
Ave
rage
Ave
rage
1/
10 H
ighe
st
Sign
ifica
nt R
ange
of
Perio
ds (S
econ
ds)
t (A
vera
ge P
erio
d)
I (Av
erag
e W
ave
Leng
th)
Min
imum
Fet
ch(N
autic
al M
iles)
Min
imum
Dur
atio
n(H
ours
)
Sea
Moderately high waves of 8 Fresh 34–40 34 19 38 5.5–18.5 9.7 322 420 30greater length; edges of Gale 36 21 44 5.8–19.7 10.3 363 500 34crests break into spindrift. 37 23 46.7 6–20.5 10.5 376 530 37The foam is blown in well 38 25 50 6.2–20.8 10.7 392 600 38marked streaks along the 40 28 58 6.5–21.7 11.4 444 710 42direction of the wind. Sprayaffects visibility.
High waves. Dense streaks 9 Strong 41–47 42 31 64 7–23 12.0 492 830 47of foam along the direction Gale 44 36 73 7–24.2 12.5 534 960 52of the wind. Sea begins to 46 40 81 7–25 13.1 590 1110 57roll. Visibility affected.
Very high waves with long 10 Whole 48–55 48 44 90 7.5–26 13.8 650 1250 63overhanging crests. The Gale 50 49 99 7.5–27 14.3 700 1420 69resulting foam is in great 51.5 52 106 8–28.2 14.7 736 1560 73patches and is blown in 52 54 110 8–28.5 14.8 750 1610 75dense white streaks along 54 59 121 8–29.5 15.4 810 1800 81the direction of the wind.On the whole, the surface ofthe sea takes a white appear-ance. The rolling of the seabecomes heavy and shock-like. Visibility is affected.
Exceptionally high waves. 11 Storm 56–63 56 64 130 8.5–31 16.3 910 2100 88(Small and medium-sized 59.5 73 148 10–32 17.0 985 2500 101ships might be lost to view behind the waves for a long time.) The sea is completely covered with longwhite patches of foam lyingalong the direction of the wind. Everywhere the edgesof the wave crests are blowninto froth. Visibility affected.
Air filled with foam and 12 Hurricane 64–71 >64 >80 >164 10–(35) (18)spray. Sea completely whitewith driving spray; visibilityvery seriously affected.
7
8
9
Dive Planning 8-7
White
Sport Diver Flag
International Code Flag"A"
International Code Flags"I and R"
International DayShapes and Lights
Red
Red
White
Yellow
Black
BlackBall
BlackDiamond
BlackBall
Shapes/Day Lights/Night
Yellow
Red
Red
White
Red
Blue
"I"
"R"
Displayed by civilian divers in the UnitedStates. May be used with code flag alpha(flag A), but cannot be used in lieu of flag A.The Coast Guard recommends that the red-and-white diver's flag be exhibited on a floatmarking the location of the divers.
Must be displayed by all vessels operatingeither in international waters or on thenavigable waters of the United States thatare unable to exhibit three shapes (see lastrow of this table). Flag A means that themaneuverability of the vessel is restricted.
"Divers are below. Boats should notoperate within 100 feet."(Varies in accordance withindividual state laws.)
"My maneuverability is restrictedbecause I have a diver down; keep wellclear at slow speed."
"I am engaged in submarine surveywork (underwater operations); keepclear of me and go slow."
"This vessel is engaged in underwateroperations and is unable to get out of the way of approaching vessels."
Displayed by all vessels in internationaland foreign waters engaged in underwateroperations.
Displayed by all vessels in international and foreign waters.
TABLE 8.2Signal Flags, Shapes, and Lights
Signal Use Meaning
8-8 NOAA Diving Manual
Currents must be considered when planning and exe-cuting a dive, particularly when using scuba. When a boatis anchored in a current, a buoyed safety line at least 100 ft.(30.5 m) in length should be trailed from the stern duringdiving operations. If, on entering the water, a diver is sweptaway from the boat by the current, the diver can use thissafety line to keep from being carried down current.
Free-swimming descents should be avoided in cur-rents, unless a means of retrieving the diver is available incase they miss their intended target. Descent from ananchored or fixed platform into water with currents shouldbe made via a down line. A trail line also should be usedunless a pickup boat is operating down current so thatdivers surfacing some distance from the entry point can beretrieved. A knowledge of changing tidal currents mayallow the diver to drift down current and to return to thestarting point on the return current.
Tidal changes often alter the direction of current andsometimes carry sediment-laden water and cause low visibil-ity within a matter of minutes. Tidal currents may preventdiving at some locations except during slack tides. Because aslack tide may be followed by strong currents, divers shouldknow the tides in the diving area and their effects.
Currents generally decrease in velocity with depth,and, therefore, it may be easier to swim close to the bottomwhen there are swift surface currents. Current directionmay change with depth, however. When there are bottomcurrents, it is recommended, whenever possible, to start theswim into the current rather than with the current; thisfacilitates the return to the entry point at the end of the divewith the current. Divers should stay close to the bottomand use rocks (if present) to pull themselves along.
Water temperature has a significant effect on the typeof equipment selected and, in some cases, determines thepractical duration of the dive. A thermocline is a boundarylayer between waters of different temperatures. Althoughthermoclines do not pose a direct hazard, their presencemay affect the selection of diving dress, dive duration, orequipment. Thermoclines occur at various depths, includ-ing levels close to the surface and in deep water.Temperature may vary from layer to layer. As much as a20°F (11C) variation has been recorded between the mixedlayer (epilimnion) above the thermocline and the deeperwaters (hypolimnion) beneath it.
Underwater visibility depends on time of day, locality,water conditions, season, bottom type, weather, and cur-rents. Frequently, divers will be required to dive in waterwhere visibility is minimal; sometimes, zero. Special precau-tions are needed. If scuba is used, a buddy line or other refer-ence system, and float are recommended. A convenient wayto attach a buddy line is to use a rubber loop that can beslipped on and off the wrist easily; this is preferable to tying aline that cannot be removed rapidly. The line should not slipoff so easily, however, that it can be lost inadvertently.
Heavy concentrations of plankton often accumulate atthe thermocline, especially during the summer and offshore
of the mid-Atlantic states. Divers may find that planktonabsorb most of the light at the thermocline and that eventhough the water below the thermocline is clear, a light isstill necessary to see adequately. Thermoclines in clearwater diffuse light within the area of greatest temperaturechange, causing a significant decrease in visibility.
WARNINGDIVERS SHOULD BE EXTREMELY CAUTIOUSAROUND UNDERWATER WRECKS OR OTHERSTRUCTURES IN LOW VISIBILITY TO AVOIDSWIMMING INADVERTENTLY INTO AN AREA WITHOVERHANGS.
A well-developed sense of touch is extremely impor-tant when working in low or zero underwater visibility.The ability to use touch cues when handling tools or instru-ments in a strange work environment is valuable to a diverin the dark. Rehearsing work functions on the surfacewhile blindfolded will increase proficiency at underwatertasks.
Underwater, low-light-level, closed-circuit televisionhas been used successfully when light levels are reduced,because a television camera “sees” more in these condi-tions than does the human eye. This is mainly true whenthe reduced visibility is caused by the absence of light; incases where the problem is caused by high turbidity, a TVcamera does not offer a significant advantage. When thepurpose of the dive is inspection or observation and aclosed-circuit television system is used, the diver servesessentially as a mobile underwater platform. The monitoris watched by surface support personnel who, in turn,direct diver movements. Underwater television cameras areavailable that are either hand held or mounted on thediver’s helmet.
Often a diver will be required to dive in water that con-tains either waterborne or sediment-contained contami-nants. The health hazards associated with polluted-waterdiving and the equipment to be used on such dives aredescribed in Chapter 13.
8.4 DIVING SIGNALS8.4.1 Hand Signals
Hand signals are used to convey basic information.There are various hand signalling systems presently in use.Divers in different parts of the country and the world usedifferent signals or variations of signals to transmit the samemessage. A set of signals used by NOAA is shown inFigure 8.2 and Table 8.4. The signals consist of hand,instead of finger, motions so divers wearing mittens canalso use them. To the extent possible, the signals werederived from those having similar meanings on land. Beforethe dive, the divemaster should review the signals shownwith all of the divers. This review is particularly importantwhen divers from different geographical areas constitute adive team, or when divers from several organizations are
Dive Planning 8-9
FIGURE 8.2Hand Signals
Stop Go Down/Going Down Go Up/Going Up Ok! Ok?
Something is Wrong
Out of Air LetÕs Buddy Breathe Danger
Distress(Need Help)
Ok! Ok?
Low on Air
8-10 NOAA Diving Manual
FIGURE 8.2Hand Signals (continued)
Me, or watch me Come here Go that way I am cold
Which direction? Yes No Take it easy, slow down
Ears not clearing Hold hands Get with your buddy Look
You lead, IÕll follow What time? What Depth? I donÕt understand
Dive Planning 8-11
cooperating in a dive. Signal systems other than hand sig-nals have not been standardized. Whistle blasts, light flash-es, cylinder taps, and hand squeezes generally are used forattracting attention and should be reserved for that purpose.
8.4.2 Surface-to-Diver Recall SignalsUnexpected situations often arise that require divers to
be called from the water. When voice communication isnot available, the following methods should be considered:
• Hammer–rapping four times on a steel hull or metalplate
• Bell–held under water and struck four times• Hydrophone–underwater speaker or sound beacon• Strobe–used at night; flashed four times
8.4.3 Line SignalsWhen using surface-supplied equipment, use line sig-
nals either as a backup to voice communications to thesurface or as a primary form of communication. Whenusing scuba, divers may use line signals in conditions ofrestricted visibility, for diver-to-diver communications orto communicate with the surface. Table 8.3 describes linesignals commonly employed.
NOTEHand or line signals may vary by geographical areaor among organizations. Divers should review sig-nals before diving with new buddies or supportpersonnel.
8.4.4 Surface SignalsIf a diver needs to attract attention after surfacing and
is beyond voice range, the following signalingdevices/methods may be used:
• Whistle (diver or scuba air powered)• Flare• Flashing strobe• Flags• Hand/arm signals• Throw water into the air
8.5 AIR CONSUMPTION RATESWhen considering air consumption rates, three terms
need definition:
• Respiratory Minute Volume ( RMV ) is the total vol-ume of air moved in and out of the lungs in oneminute.
• Actual cubic feet (acf ) is the unit of measure thatexpresses actual gas volume in accordance with theGeneral Gas Law.
• Standard cubic feet (scf ) is the unit of measureexpressing surface equivalent volume, under stan-dard conditions,* for any given actual gas volume.
TABLE 8.3Line Pull Signals forSurface-to-Diver Communication
*Standard conditions for gases are defined as 32¡F(0C), 1 ata pressure, and dry gas.
8-12 NOAA Diving Manual
In computing air consumption rate, the basic deter-minant is the respiratory minute volume, which is direct-ly related to exertion level and which, because ofindividual variation in physiological response, differsamong divers (Cardone 1982). See Table 8.5.Physiological research has yielded useful estimates ofrespiratory minute volumes for typical underwater situa-tions likely to be encountered by most divers (U.S. Navy1985). Table 8.6 shows these estimates. These estimatesof respiratory minute volumes apply to any depth andare expressed in terms of actual cubic feet, or liters, perminute (acfm or alpm, respectively).
The consumption rate at depth can be estimated bydetermining the appropriate respiratory minute volume forthe anticipated exertion level and the absolute pressure ofthe anticipated dive depth. This estimate, expressed in stan-dard cubic feet per minute (scfm), is given by the equation:
Cd = RMV (Pa)
whereCd = consumption rate at depth in scfm
RMV = respiratory minute volume in acfmPa = absolute pressure (ata) at dive depth
Problem:Compute the air consumption rate for a 50 ft. (15.2
m) dive requiring moderate work, maximum walkingspeed, hard bottom.
Solution:Cd = RMV (Pa)
RMV = 1.1 acfm (from Table 8.5)Pa 50/33 + 1 = 2.51 ata
Cd = (l.l acfm)(2.51 ata) = 2.76 scfm
Signal
Hand raised, fingers pointed up, palm toreceiver
Thumb extended downward from clenchedfist
Thumb extended upward from clenched fist
Thumb and forefinger making a circle withthree remaining fingers extended (if possi-ble)
Two arms extended overhead with finger-tips touching above head to make a largeÒOÓ shape
Hand flat, fingers together, palm down,thumb sticking out, then hand rocking backand forth on axis of forearm
Hand waving over head (may also thrashhand on water)
Fist pounding on chest
Hand slashing or chopping throat
Fingers pointing to mouth
Clenched fist, arms extended and forminga ÒXÓ in front of chest
Comment
Transmitted in the same way as a Traffic PolicemanÕsSTOP
Divers wearing mittens may not be able to extendthree remaining fingers distinctly (see various draw-ings of signal)
A diver with only one free arm may make this signalby extending that arm overhead with fingertips touch-ing top of head to make the ÒOÓ shape. Signal is forlong-range use
This is the opposite of OK! The signal does not indi-cate an emergency
Indicated immediate aid required
Indicates air supply is reduced to the quantity agreedupon in predive planning or air pressure is low andhas activated reserve valve
Indicates that signaler cannot breathe
The regulator may be either in or out of the mouth
TABLE 8.4Hand Signals
Meaning
STOP
GO DOWN orGOING DOWN
GO UP orGOING UP
OK! or OK?
OK! or OK?
SOMETHINGISWRONG
DISTRESS
LOW ON AIR
OUT OF AIR
LETÕS BUDDYBREATHE
DANGER
Dive Planning 8-13
TABLE 8.5Respiratory Minute Volume (RMV) at Different Work Rates
SLOW WALKING ON HARD BOTTOM UNDER WATERSWIMMING, 0.5 KNOT (SLOW)
SLOW WALKING ON MUD BOTTOM UNDER WATERSWIMMING, 0.85 knot (av. speed)MAX. WALKING SPEED, HARD BOTTOM U/W
SWIMMING 1.0 KNOTMAX. WALKING SPEED, MUD BOTTOM U/W
SWIMMING, 1.2 KNOTS
1216
202630
3535
53
0.420.60
0.710.921.1
1.21.2
1.9
Actual cubic ft / min (STP)Actual liters / min (STP)Activity Respiratory Minute Volume
LIGHTWORK
MODERATEWORK
HEAVYWORK
SEVEREWORK
19
20
22
23
24
26
27
28
29
31
32
33
35
36
37
39
40
41
42
44
45
46
48
49
50
52
1516171819202122232425262728293031323334353637383940
10 15 20 25 30 40 50 60 70 80 90 100 120 140 16021
23
24
26
27
29
30
31
33
34
36
37
39
40
42
43
45
46
47
49
50
52
53
55
56
58
24
25
27
28
30
32
33
35
36
38
40
41
43
44
46
48
49
51
52
54
56
57
59
60
62
64
27
28
30
32
34
36
37
39
41
43
45
46
48
50
52
54
55
57
59
61
63
64
66
68
70
72
28
30
32
34
36
38
39
41
43
45
47
49
51
53
55
57
58
60
62
64
66
68
70
72
74
76
33
35
37
39
41
44
46
48
50
52
55
57
59
61
63
66
68
70
72
74
77
79
81
83
85
88
37
40
42
45
47
50
52
55
57
60
62
65
67
70
72
75
77
80
82
85
87
90
92
95
97
100
42
44
47
50
53
56
58
61
64
67
70
72
75
78
81
84
86
89
92
95
98
100
103
106
109
112
46
49
52
55
58
62
65
68
71
74
77
80
83
86
89
93
96
99
102
105
108
111
114
117
120
124
51
54
57
61
64
68
71
74
78
81
85
88
91
95
98
102
105
108
112
115
119
122
125
129
132
136
55
59
62
66
70
74
77
81
85
88
92
96
99
103
107
111
114
118
122
125
129
133
136
140
144
148
60
64
68
72
76
80
84
88
92
96
100
104
108
112
116
120
124
128
132
136
140
144
148
152
156
160
69
73
78
82
87
92
96
101
105
110
115
119
124
128
133
138
142
147
151
156
161
165
170
174
179
184
78
83
88
93
98
104
109
114
119
124
130
135
140
145
150
156
161
166
171
176
182
187
192
197
202
208
87
92
98
104
110
116
121
127
133
139
145
150
156
162
168
174
179
185
191
197
203
208
214
220
226
232
TABLE 8.6Air Consumption Table at Depth
DEPTH (FEET)
SUR
FAC
E A
IR C
ON
SUM
PTIO
N R
ATE
(PSI
PER
MIN
UTE
)
Surf
ace
8-14 NOAA Diving Manual
8.5.1 Determining Individual Air Utilization RatesAn alternative approach that can be used expresses
air utilization rates in terms of pressure drop in poundsper square inch (psi) rather than respiratory minute vol-ume. Keep in mind that usable cylinder pressure isdefined as the beginning cylinder pressure minus recom-mended air reserve (see Table 8.6). This technique allowsdivers to determine their Surface Air Consumption(SAC) rate which can be used to calculate estimated airconsumption rate at any depth. To determine the rate,read the submersible pressure gauges at the beginningand end of a dive to a constant depth. These readingsgive the information needed to use the simple four-stepprocedure shown below:
1. Subtract ending psi (as read from the submersiblepressure gauge) from the beginning psi to deter-mine the amount of air used during the timed dive(∆ psi).
2. Using the following formula, determine the diver’ssurface air consumption (SAC) rate:
∆psi/time (min) psi per minute on the surface (SAC)=
(depth in ft + 33)/33
3. Find the psi per minute on the surface on the leftside of the Air Consumption Table (Table 8.6) thatis closest to the estimated psi per minute. Readacross to the desired depth, which will give the esti-mated air consumption rate at depth.
4. To estimate how many minutes a cylinder of airwill last at that depth, divide the number of usablepsi in the cylinder (as shown on the submersiblepressure gauge minus a reserve amount) by the psiper minute used at that depth.
Problem:A diver swims a distance at 30 ft. (9.1 m) in ten min-
utes; the submersible pressure gauge reads 2,350 psi at thestart and 2,050 at the end of the timed dive, showing that atotal of 300 psi was consumed. What is the diver’s SAC?
The basic equation is:
∆psi/time (min)
(depth in ft + 33)/33
Solution:
300 (psi) ÷ 10 (mins) =
30 =
30 = 15.7 psi/min
(30 (depth) + 33)/33 (63/33) 1.9
The diver would consume 15.7 psi per minute at the sur-face. Knowing the consumption rate at the surface allows
the diver to use Table 8.6 to find the rate at any depth.The same information can be determined by multiplyingthe SAC figure times the depth of the planned dive inatmospheres absolute.
It is important to understand that individuals varysomewhat from day to day in their air consumption rates,and these calculations should thus be considered esti-mates only (Cardone 1982).
Problem:Convert SAC to cubic feet per minute (CFM) by mul-
tiplying the diver’s SAC times the cylinder constant (k)using formula:
RMV = SAC × k
Solution:The diver in this example had a SAC of 15.71 psi/min
using a scuba cylinder with a k factor of 0.0267 ft3/psi.
RMV= SAC × kRMV= 15.71 psi/min × 0.0267 ft3/psiRMV= 0.42 ft3/min
8.5.2 Scuba DurationKnowing the probable duration of the scuba air sup-
ply is vital to proper dive planning. With scuba, the dura-tion of the available air supply is directly dependent onthe consumption rate. Scuba air supply duration can beestimated using the equation:
Da =Va
Cdwhere
Da = duration in minutes Va = available volume in scf Cd = consumption at depth in scfm
The available volume depends on the type (rated vol-ume and rated pressure) and number of cylinders used,the gauge pressure measured, and the recommended min-imum cylinder pressure. Consumption rate depends onthe depth and the exertion level of the dive.
The “standard 80 cubic foot” aluminum cylinder hasan internal volume of 0.399 cubic feet (11.3 liters) at oneatmosphere. At its rated pressure of 3,000 psig, the cylin-der contains a deliverable volume of 81.85 cubic feet(2,317.7 liters).
For a given scuba cylinder, the ratio of rated vol-ume to rated pressure is a constant (k = Vr/Pr), mean-ing that a constant volume of air is delivered for eachunit of cylinder pressure drop. Mathematically, thisresults in a linear relationship between gauge pressureand deliverable volume. Figure 8.3 shows this relation-ship for a 71.2 ft3 (2,016 liters) steel cylinder and an 80ft3 (2,266 liters) aluminum cylinder. Deliverable vol-umes at any gauge pressure for these two cylinder types
SAC =
Dive Planning 8-15
can be read directly from Figure 8.3, or they can beindividually computed using the equation:
Vd = Pg x k
whereVd = deliverable volume in scfPg = gauge pressure in psig
k = cylinder constant
This equation can be used for any type of cylinder;see Table 8.7 for the appropriate cylinder constant.
For planning purposes, the available volume of air isthe difference between the deliverable volume at a givencylinder pressure and the recommended minimum cylin-der pressure. The recommended minimum cylinder pres-sures for the two most commonly used scuba cylindertypes are shown in Table 8.8. The available volume of airin the diver’s supply can be determined by the equation:
Va = N(Pg - Pm)k
whereVa = available volume in scfN = number of cylinders
Pg = gauge pressure in psigPm = recommended minimum pressure in psig
k = cylinder constant
For planning purposes, estimates of cylinder durationare based on available air volumes rather than deliverableair volumes.
Problem:Estimate the duration of a set of twin 80 ft3 (2,318 liters)
aluminum cylinders charged to 2,400 psig for a 70 ft. (21.3m) dive for a diver with a RMV of 0.6 acfm.
Solution:The basic equation for duration is:
Da =Va
Cdwhere
Da = duration in minutesVa = available volume in scfCd = consumption rate at depth in scfm
Step 1:Determine Va using:
Va = N(Pg - Pm)kVa = 2(2,400 psig - 600 psig) (0.0266 scf/psig)
= 2(1,800 psig) (0.0266 scf/psig)= 95.76 scf
Step 2:Determine Cd using:
Cd = RMV (Pa)where
RMV = respiratory minute volume in acfmPa = absolute pressure at dive depth
Cd = 0.6 acfm 70 + l
33= 1.87 acfm
( )
FIGURE 8.3Deliverable Volumes at Various Gauge Pressures
TABLE 8.7Cylinder Constants
8-16 NOAA Diving Manual
Step 3:Solve the basic equation for Da:
Da = VaCd
=95.76 scf
1.87 scfm
= 51.2 minutes
Table 8.9 shows estimates of the duration of a single alu-minum 80 ft3 (2,318 l ) cylinder at five exertion levels for vari-ous depths. These estimated durations are computed onthe basis of an available air volume of 64.1 ft3 (Va = 3,000psig - 600 psig) (0.0267 ft3/psig).
8.5.3 Scuba Air RequirementsTotal air requirements should be estimated when
planning scuba operations. Factors that influence thetotal air requirement are depth of the dive, anticipatedbottom time, normal ascent time at 30 ft/min (9.1m/min), any required stage decompression time, andconsumption rate at depth. For dives in which directascent to the surface at 30 ft/min (9.1 m/min) is allow-able, the total air requirement can be estimated using theequation:
TAR = tdt (Cd)
where TAR = total air requirement in scf
tdt = total dive time in minutes(bottom time plus ascent time at 30 ft/min)
Cd = consumption rate at depth in scfm
Problem 1:Estimate the total air requirements for a 30-minute
dive to 60 ft. (18.3 m) for a diver with a RMV of .92acfm.
Solution:Step 1:
Determine tdt. Total dive time is defined as the sumof the bottom time and normal ascent time at 30 ft/min(9.1 m/min):
tdt = 30 + 2 = 32 mins
Step 2:Determine Cd using the equation:
Cd = RMV (Pa)RMV = 0.92 acfm
60Pa = + 1 = 2.81 ata33
Cd = (0.92 acfm) (2.81 ata)= 2.59 scfm
TABLE 8.8Scuba Cylinder Pressure Data
TABLE 8.9Estimated Duration of 80 Ft3 Aluminum Cylinder
500500
22503000
24753000
Steel 72Aluminum 80
430600
29.114.69.77.35.84.8
42.721.414.210.78.57.1
58.329.219.414.611.79.7
91.645.830.522.918.315.3
256.4128.285.564.151.342.7
1.02.03.04.05.06.0
0336699
132165
ata ** *
*
**
Step 3:Determine TAR using the equation:
TAR = tdt (Cd)= (32 mins) (2.59 acfm)= 82.88 scf
For dives in which stage decompression will be neces-sary, the total air requirement can be estimated using theequation:
TAR = Cd (BT + AT) + Cd1T1 + Cd2T2 + Cd3T3 (etc.)
where Cd1T1, Cd2T2, are the air consumption rates andtimes at the respective decompression stops.
Problem 2:Estimate the total air requirement for an 80-minute diveto 60 ft. (18.3 m) for a diver with a RMV of 0.6 acfm.
Solution:Step 1:Determine Cd and Cd1 using the equation:
Cd = RMV (Pa)= (0.6 acfm) (2.8 ata) = 1.68 scfm
Step 2:Determine the total time for the dive, ascent, and
decompression stops. For the dive and ascent to the sur-face, add the bottom time (BT) and the ascent time(AT) (to the nearest whole minute) at 30 ft/min (9.1m/min).
BT + AT = 80 + 2 = 82 mins
This dive requires a 10-ft. decompression stop. At anascent rate of 30 ft/min, it will take two minutes toascend from 60 ft. (18.3 m) to the surface.
The time required for decompression at 10 ft. (3 m)is 7 minutes, according to the USN Standard AirDecompression Table for a dive to 60 ft. for 80 min-utes.
Cd1 = 0.6 10
+ 1 = 0.78 scfm33
(Assume same RMV on decompression stop.)
Step 3:Determine TAR using the equation for this case:
TAR = Cd (BT + AT) + Cd1T1= (1.68 scfm) (62 mins) + (0.78 scfm) (7 mins)= 104.2 + 5.5 = 109.7 scf
Computation of these estimates during predive plan-ning is useful to decide whether changes in assigned tasks,task planning, etc. are necessary to ensure that the divecan be conducted with the available air supply. However,positioning an auxiliary cylinder at the decompressionstop is considered a safer practice than relying on calcula-tions of the available air supply.
8.5.4 Surface-Supplied Air RequirementsEstimations of air supply requirements and duration of
air supplies for surface-supplied divers are the same as thoseof scuba divers except when free-flow or free-flow/demandbreathing systems are used; in these cases, the flow, in actu-al cubic feet per minute is used (in all calculations) insteadof RMV (see Table 8.10). Also, the minimum bank pressuremust be calculated to be equal to 220 psig plus the absolutepressure of the dive (expressed in psia).
Problem:Estimate the air requirements for a 90 ft. (27.4 m)
dive for 70 minutes with a demand/free-flow helmet. Thisdive requires decompression stops of seven minutes at 20ft. (6.1 m) and 30 minutes at 10 ft. (3 m).
Solution:
TAR = Cd (BT + AT) + Cd1T1 + Cd2T2where
TAR = Total Air RequirementCd = Consumption rate at depth (scfm)BT = Bottom time (mins)AT = Ascent timePa = Pressure in ata
Step 1:Determine Cd, Cd1, Cd2:
Cd = flow x Pa= (1.5 acfm)(3.73 ata) = 5.6 scfm
Cd1 = (1.5 acfm)(1.61 ata) = 2.4 scfmCd2 = (1.5 acfm)(l.30 ata) = 2.0 scfm
Step 2:TAR = Cd (BT + AT) + Cd1 T1
= 5.6 scf (70 + 3 mins) + 2.4 scf (7 mins) + 2.0 scf (30 mins)
= 409 scf + 17 scf + 60 scf= 486 scf
Cylinder constants for large high-pressure air/gas stor-age systems are determined in the same fashion as thosefor scuba cylinders, i.e., rated volume/rated pressure = k.
The procedure for determining available volume ofair is also the same as for scuba. For example,
Va = N(Pg - Pm) k
Dive Planning 8-17
( )
whereVa = available volume (scf)N = number of cylinders
Pg = gauge pressure (psig)Pm = minimum reserve pressure (psig)
k = cylinder constant
NOTEIf cylinder banks are used as a back-up to a com-pressor supply, the bank must be manifolded withthe primary source so that an immediate switchfrom primary to secondary air is possible (seeFigure 6.10).
Problem:Determine the number of high-pressure air cylinders
required to supply the air for the above dive (486 scf ) ifthe rated volume equals 240 scf, rated pressure equals2,400 psi, and beginning pressure equals 2,000 psi, using aminimum reserve pressure of 220 psi.
Solution:
Step 1:How much air could be delivered from each cylinder?
Va = N(Pg - Pm)k
240 scfk = = 0.1 scf/psi
2,400 psi
Pm = 220 psi + 90 + 33 × 14.7 = 275 psi33
Va = 1(2,000 - 275) × 0.1Va = 172.5 scf/cylinder
Step 2:How many cylinders would be required in the bank to sup-ply the required amount of gas?
vol. required 486 scfN = = = 2.8 or 3 cylinders
vol/cyl 172.5 scf/cyl
NOTECalculations for gas supply requirements or scubaduration are for planning purposes only. The diverand tender must continuously monitor the gassupply throughout the dive.
8-18 NOAA Diving Manual
TABLE 8.10Flow-Rate Requirements for Surface-Supplied Equipment
Equipment Type
Demand/freeflowFree flow
Flow Rate
1.5 acfm6.0 acfm
NOTE: Significant variations in these values canoccur, depending on the flow-valve set by the diver.Therefore, these values are minimum estimates.
( )
The NOAA Diving Manual was prepared jointly by the National Oceanic andAtmospheric Administration (NOAA), U.S. Department of Commerce and BestPublishing Company.
This CD-ROM product is produced and distributed by the National Technical InformationService (NTIS), U.S. Department of Commerce.Visit our Web site at www.ntis.gov.