Dive planning

Commercial diving contractors will develop specifications for the operation in cooperation with the client, who will normally provide a specific objective. The client will generally specify what work is to be done, and the diving contractor will deal with the logistics of how to do it.[3]

Other professional divers will usually plan their diving operations around an objective related to their primary occupation.[5]

Recreational divers will generally choose an objective for entertainment value, or for training purposes.

It will generally be necessary to specify the following:

• Work to be done, or the recreational equivalent
• Equipment needed
• Procedures to be used
• Personnel required
• Places
• Times

• Expected surface conditions, such as sea state, air temperature, and wind chill factor
• Expected underwater conditions, including water temperature, depth, type of bottom, tides and currents, visibility, extent of pollution, and other hazards
• Assistance and emergency information, including location, status, and contact procedures for the nearest recompression chamber, evacuation and rescue facilities, and nearest hospital.
• Location and accessibility of the site

Detailed planning depends on the mode and techniques selected for the dive, and the choice of these depends to a large extent on the physical constraints of the dive, but also to the legal, financial and procedural constraints of the divers. The mode and techniques chosen must also allow the dive to be done at an acceptable level of risk. There is usually more than one mode which is physically feasible, and often a choice between modes which are otherwise acceptable. In some cases detailed planning may show that the initial choice was not appropriate, and the process has to be repeated for an alternative choice.[6][5]

Surface supplied diving

Surface supplied diving using a diving stage

Breathing gases may be supplied from the surface through a diver's umbilical, or airline hose, which provides breathing gas, communications and a safety line, with options for a hot water hose for heating, a video cable and gas reclaim line. The diver's breathing gas supply is significantly more secure than for scuba; communications are simplified and the divers position is either known or can be traced reliably by following the umbilical. Several major risks are thereby mitigated, but the system also has serious disadvantages in some applications, as diver mobility is constrained by the length of the umbilical, and it may snag on obstructions.

Surface-oriented, or bounce diving, is how commercial divers refer to diving operations where the diver starts and finishes the diving operation at atmospheric pressure. The alternative, while retaining surface supply, is saturation diving. For bounce dives, the diver may be deployed directly, often from a diving support vessel or indirectly via a diving bell.[7] Decompression procedures include in-water decompression or surface decompression in a deck chamber. Small closed bell systems which include a two-man bell, a launch and recovery frame and a chamber for decompression after transfer under pressure (TUP) are reasonably mobile, and suited to deep bounce dives.[7]

Saturation diving

Diver Transfer Capsule suitable for saturation diving

Saturation diving lets divers live and work at depth for days or weeks at a time. After working in the water, divers are transferred in a closed diving bell to rest and live in a dry pressurized underwater habitat on the bottom or a saturation life support system of pressure chambers at the surface. Decompression at the end of the dive may take many days, but since it is done only once for a long period of exposure, rather than after each of many shorter exposures, the overall risk of decompression injury to the diver and the total time spent decompressing are reduced. This type of diving allows greater economy of work and enhanced safety, but the capital and running costs are high and the systems are expensive to transport. Mobility of the diver is restricted because of the umbilical.[8]

Atmospheric diving suits

Diver in atmospheric diving suit on launch and recovery platform

Atmospheric diving suits can be used for very deep dives of up to 2,300 feet (700 m) for many hours, and eliminate several physiological dangers associated with deep diving: the occupant need not decompress; there is no need for special gas mixtures; and there is no danger of decompression sickness or nitrogen narcosis. Disadvantages include high cost, limited availability, bulk and limited diver dexterity.

The diving team personnel selection will depend largely on the diving mode selected and organisational requirements.

Professional dive team members will generally be selected on documented evidence of proven competence or qualification for the tasks allocated. Professional diving teams will usually include (the precise terminology may vary between organisations):[5][9]

• A supervisor
• One or more working divers
• One or more stand-by divers
• One or more diver's attendants
• Other surface support personnel, which may include:
  • Medical support (not necessarily on-site)
  • Chamber operator or life support technician
  • Support vessel crew
  • Equipment technicians, gas panel operators, timekeepers, riggers

Technical teams will also generally base appointments on proven competence, certification or personal trust. Technical diving groups vary in complexity, but will generally comprise:

• Dive team
• In-water support team
• Surface support team

Recreational groupings may be based on personal experience and trust, but are frequently relatively arbitrary allocations by the service provider, based on certification. Recreational diving groups commonly comprise a buddy pair of divers, but may also be a solo diver or a group of divers who will be led by a divemaster. Selection may be by mutual agreement to dive together, or may simply be the result of booking on the same dive.

Depth is often one of the more straightforward parameters, as it is often fixed by the topography of the site.

Time is influenced by limitations of equipment and decompression constraints, as well as the actual time required to perform the intended task, which in turn is influenced by the underwater environment in general, and specific to the site.

The specific diving environment must be taken into account during dive planning. The environment at the dive site will determine several factors which may require specific planning, such as the depth, water salinity and altitude which affect decompression planning, an overhead environment affects navigation and gas planning, water temperature and contaminants affect the choice of exposure and environmental protection, site topography affects choice of entry and exit points.

Divers face specific physical and health risks when they go underwater with diving equipment, or use high pressure breathing gas.

A hazard is any biological, chemical, physical, mechanical or environmental agent or situation that poses a level of threat to life, health, property, or environment. The presence of a combination of several hazards simultaneously is common in diving, and the effect is generally increased risk to the diver, particularly where the occurrence of an incident due to one hazard triggers other hazards with a resulting cascade of incidents.

Diving hazards may be classified under several groups:

• The aquatic environment itself
• Use of breathing equipment underwater
• Exposure to a pressurised environment and pressure changes
  • Pressure changes during descent
  • Pressure changes during ascent
  • Breathing gases at high ambient pressure
• The specific diving environment
• Pre-existing physiological and psychological conditions in the diver
• Diver behaviour and competence
• Failure of diving equipment other than breathing apparatus
• Hazards of the dive task and special equipment

The planned dive profile is an important input parameter for gas planning and decompression planning, and is generally based on the time required to perform the task of each specific dive, and the depth at which the task will be performed, in combination with environmental considerations and the breathing gas mixtures chosen. Limits are often due to exposure to cold, work load, decompression time, safety constraints and logistics of breathing gas supply.[2][5]

For some dives the route to be followed and navigation procedures to follow the planned route may be important, either for achieving the objective, for safety, or for both. There may be known hazards that can be avoided by following a specific route or constraining the possible extent of diver excursion.

In all penetration dives the route may be critical for safety. The diver must be assured of getting out from the overhead zone before running out of gas. The standard method is to follow a guideline into and out of the overhead environment, and laying the line or laying and recovering the line may be part of the dive plan. In explorations and surveys the route may be unknown or uncertain, and contingency plans must be known to the divers so that the dive plan can be altered to suit the situation as it unfolds.

Professional divers may follow a planned route to the worksite which prevents the diver from close approach to known hazards. This may involve limiting umbilical length and manned or unmanned underwater tending points, downlines and jackstays

Diving equipment in storage

Equipment will be chosen based on several constraints, including:[10][5][9]

• Legal and procedural requirements of the organisation
• Availability of equipment
• Diver skills and certification
• Suitability for the purpose
• Risk and benefit considerations

Equipment and supplies selection would normally include:[5]

• Diving equipment
• Breathing gas, including a backup supply
• Tools or equipment for the task if appropriate
• Dive platform and support equipment, including diver/crew shelter
• Oxygen resuscitator and first aid kit
• Dive flag
• Communications equipment

A recreational diver may expect many of these items to be arranged by the service provider (the dive boat operator, shop, or school providing thansport to the dive site and organising the dive).

Decompression tables for recreational dive planning

Decompression is planned based on the intended dive profile, the chosen gas mixtures, and the chosen decompression tables or algorithms.[10][5]

There are two basic approaches to decompression for surface oriented dives, and one for saturation diving.

• Real time computation of tissue gas levels and the appropriate decompression schedule may be monitored by personal decompression computers worn by the diver. This system is popular with recreational, technical and scientific scuba divers. Any deviation from the planned profile is automatically taken into account, and the diver can keep track at all times of the current total time required for ascent. The surface team is not aware of the decompression status of a diver unless there is voice communication and the diver reports the information.[10][5]
• Decompression schedules are drawn up for the planned dive profile before the dive from tables or a program. Contingency schedules are usually prepared for scuba divers, which allow for all the reasonably probable deviations from the planned schedule, and usually allow for variations in depth and time. These schedules are carried by the diver and used to manage the ascent profile and decompression.[10] Surface supplied divers are monitored by the surface team, and if they deviate from plan the supervisor can change the schedule to suit.[9][6]
• Saturation diving will decompress the divers only at the end of the diving contract, in the controlled and relatively comfortable environment of the saturation system. The schedule will depend on the pressure and breathing gas mixture, not on the duration of exposure.[8]

The procedures chosen will to a large extent depend on the mode of diving and equipment available.[6]

Gas planning for diving operations where divers use open circuit equipment with breathing gas mixtures is more complex than operations where atmospheric air is supplied via low pressure compressor from the surface, or the breathing gas is reclaimed, processed and re-used.[11][9][5]

Scuba gas planning

Main article: Scuba gas planning

Gas blending equipment

Scuba gas planning is the aspect of dive planning which deals with the calculation or estimation of the amounts and mixtures of gases to be used for a planned dive profile, and can be critical to the safety of the dive. The scuba diver by definition is independent of surface supply and, in general, must carry all gas needed for the dive, though in limited circumstances depots of drop cylinders may be placed along the route of the dive for use on the return. This requires the route to be marked and the divers to return along the marked route, and is particularly suited to penetration dives, such as wreck and cave dives.[10]

Deep dives with open water ascents can also occasionally make use of surface standby divers who can provide contingency gas to ascending divers whose position is marked by a shotline or decompression buoys.[2]

The calculations assume that the dive profile, including decompression, is known, but the process may be iterative, involving changes to the dive profile as a consequence of the gas requirement calculation, or changes to the gas mixtures chosen.[10][5]

Scuba gas planning includes the following aspects:[10][5]

• Choice of breathing gases
  • to limit decompression requirements
  • to limit inert gas narcosis
  • to limit work of breathing
• Choice of Scuba configuration
• Estimation of gas quantities required for the planned dive, including bottom gas, travel gas, and decompression gases, as appropriate to the profile.
• Estimation of gas quantities for reasonably foreseeable contingencies.
• Choice of cylinders to carry the required gases. Each cylinder volume and working pressure must be sufficient to contain the required quantity of gas.
• Calculation of the pressures for each of the gases in each of the cylinders to provide the required quantities.
• Specifying the critical pressures of relevant gas mixtures for appropriate stages (waypoints) of the planned dive profile.

Contingency planning covers what to do if something happenes that is not according to the planned operation. The hazard identification and risk assessment will suggest the range of foreseeable contingencies, and the specifics of how much to organise to deal with them will depend on the consequences.[10]

In general, contingencies that have serious health and safety consequences should have plans in place to deal with them, while those which are merely an inconvenience may be accepted if they occur.[9][5]

Some contingency classes are listed here:

• Environmental condition changes
  • Weather and sea state
• Equipment malfunctions
• Incorrect information
  • Position of site
  • Accessibility
  • Environmental conditions
  • Unexpected hazards
  • Extent of work, equipment required

Plans for technical contingencies may include arrangements for alternative equipment, spares, alternative boat etc. The level of contingency planning will depend on the project, and the importance of the task. Plans for adverse conditions may include arrangements for alternative dates, or in some cases alternative venues.[9][5]

In general, there should be plans to deal with reasonably foreseeable emergencies that pose a risk to health and safety wherever there is a duty of care, these may include where relevant:[9][5]

• First Aid for medical emergencies
• Search and recovery
• Casualty evacuation
• Site evacuation
• Hazmat emergencies

Some of the action generally taken to prepare for possible medical emergencies will include:[9][5]

• Appropriate first aid equipment available on site
• Adequate oxygen administration equipment available on site
• A plan for evacuation of a casualty to a hyperbaric chamber
• A list of contact numbers, call codes and frequencies for local emergency services.
• How to reach the nearest suitable emergency medical facility from the site.

It may be necessary to arrange for clearance to dive. Permits or permission for access or to dive at the site may be required, and making the arrangements can be considered part of dive planning.[9][5]

This may include, but is not limited to:[9][5]

• Permits to dive in a Marine Protected Area
• Permits to collect specimens at a specific site or in general.
• Permits to use specific collecting methods.
• Permits to operate specific equipment.
• Permits to dive on an archaeological site.
• Permits to perform salvage work.
• Permits to perform blasting work.
• Permits or permission to launch or recover a vessel at a specific place.
• Permits to operate a vessel in restricted areas.
• Permission from harbourmaster to dive within harbour limits.
• Permission from port control to dive in shipping lanes.
• Permission from landowners to access the water, and to dive in inland waters.
• Permission from utilities companies to dive in reservoirs.
• Clearance from vessel operators or installation operators that the site is safe to dive.
• Clearance that contamination is acceptable for the diving equipment to be used. This may require a water sample to be tested before the dive.

• Travel to the site
• Preparation of diving and support equipment
• Predive briefing
• Actual diving operations
• Recovery, cleaning, inspection, repair, and storage of gear
• Debriefing

Estimating the cost of a diving operation is an important component of the planning process,[10] and is dependent on almost all the factors described above.