Dive planning


Dive planning is the process of planning an underwater diving operation. The purpose of dive planning is to increase the probability that a dive will be completed safely and the goals achieved. Some form of planning is done for most underwater dives, but the complexity and detail considered may vary enormously.
Professional diving operations are usually formally planned and the plan documented as a legal record that due diligence has been done for health and safety purposes. Recreational dive planning may be less formal, but for complex technical dives, can be as formal, detailed and extensive as most professional dive plans. A professional diving contractor will be constrained by the code of practice, standing orders or regulatory legislation covering a project or specific operations within a project, and is responsible for ensuring that the scope of work to be done is within the scope of the rules relevant to that work. A recreational diver or dive group is generally less constrained, but nevertheless is almost always restricted by some legislation, and often also the rules of the organisations to which the divers are affiliated.
The planning of a diving operation may be simple or complex. In some cases the processes may have to be repeated several times before a satisfactory plan is achieved, and even then the plan may have to be modified on site to suit changed circumstances. The final product of the planning process may be formally documented or, in the case of recreational divers, an agreement on how the dive will be conducted. A diving project may consist of a number of related diving operations.
A documented dive plan may contain elements from the following list:
  • Overview of diving activities
  • Schedule of diving operations
  • Specific dive plan information
  • Budget

    Objective

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

    Analysis of available information on the site

  • 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

    Selection of techniques and mode of diving

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.

Diving without breathing apparatus

does not involve the use of external breathing devices, but relies on a diver's ability to hold his or her breath until resurfacing. Free diving is limited in depth and time, but for some purposes it may be suitable.

Scuba diving

with a self-contained underwater breathing apparatus, which is completely independent of surface supply, provides the diver with the advantages of mobility and horizontal range far beyond what is possible when supplied from the surface by the umbilical hoses of surface-supplied diving equipment. Scuba has limitations of breathing gas supply, communications between diver and surface are problematic, the location of the diver may be difficult to monitor, and it is considered a higher-risk mode of diving in most circumstances. Scuba is specifically forbidden for some professional applications. Decompression is often avoided, and if necessary, is generally in-water, but may use a variety of gases.

Open circuit

discharge the breathing gas into the environment as it is exhaled, and consist of one or more diving cylinders containing breathing gas at high pressure connected to a primary diving regulator, and may include additional cylinders for decompression gas or emergency breathing gas.

Rebreathers

allow recycling of exhaled gases. This reduces the volume of gas used, so that a smaller cylinder, or cylinders, than open-circuit scuba may be used for the equivalent dive duration, and giving the ability to spend far more time underwater compared to open circuit for the same gas consumption. Rebreathers also produce far less bubble volume and less noise than open circuit scuba, which makes them attractive to military, scientific and media divers. They also have a larger number of critical failure modes, are more expensive and require more maintenance and require more training to use at a reasonable level of safety.

Surface supplied diving

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. Decompression can be by in-water decompression or surface decompression in a deck decompression chamber. Small closed bell systems which include a two-man bell, a launch and recovery frame and a deck chamber for decompression after transfer under pressure are reasonably mobile, and suited to deep bounce dives.

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.

Atmospheric diving suits

can be used for very deep dives of up to 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.

Diving team selection

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. The precise terminology may vary between organisations, but professional diving teams will usually include:
Technical teams will also generally base appointments on proven competence, certification or personal trust. Technical diving groups vary in complexity, but will generally comprise:
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 and time

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.
Together, the depth and time constitute the planned dive profile, which is needed for decompression planning and [|gas planning].