Underwater work


Underwater work is work done underwater, generally by divers during diving operations, but includes work done underwater by remotely operated underwater vehicles and crewed submersibles.
Underwater work is the activity required to achieve the purpose of the diving operation additional to the activities required for safe diving in the specific underwater environment of the worksite, including finding and identifying the workplace, and where necessary, making it safe to do the planned work. Some of these activities have a wide range of applications in work suitable for a given diving mode, and are likely to be considered basic skills and learned during professional diver training programmes for the relevant mode. Others are specialist skils and are more likely to be learned on the job or on skills training programmes not directly related to diving.

Occupational diving fields

There are several occupational specialty fields in occupational diving, and the work done in them may overlap.
There are several kinds of skill that may be needed in underwater work by occupational divers in various fields, and are often learned during entry level training.

Underwater navigation

  • Pilotage involves navigation by naturally observable landmarks and phenomena, such as sunlight, water movement, bottom composition, bottom contour and noise. Although natural navigation is taught on courses, developing the skills is generally more a matter of experience.
  • Compass navigation is a matter of training, practice and familiarity with the use of underwater compasses, combined with various techniques for reckoning distance underwater, including kick cycles, time, and occasionally by actual measurement, which may involve the length of umbilical deployed. Kick cycles depend on the diver's finning technique and equipment, but are generally more reliable than time, which is critically dependent on speed. Techniques for direct measurement also vary, from the use of calibrated distance lines or surveyor's tape measures, to a mechanism like an impeller log, to pacing off the distance along the bottom with the arms.
  • Use of a guide line or jackstay. A guide line may be laid to facilitate navigation to and from the underwater workplace. This allows divers to travel to and from the workplace with minimal delay, even in poor visibility. A jackstay serves the same purpose in heavy duty format.

    Underwater searches

Underwater searches are procedures to find a known or suspected target object or objects in a specified search area under water. They may be carried out underwater by divers, crewed submersibles, remotely operated underwater vehicles, or autonomous underwater vehicles, or from the surface by other agents, including surface vessels, aircraft and cadaver dogs.
A search method attempts to provide full coverage of the search area. This is greatly influenced by the width of the sweep which largely depends on the method used to detect the target. For divers in conditions of zero visibility this is as far as the diver can feel with his hands while proceeding along the pattern. When visibility is better, it depends on the distance at which the target can be seen from the pattern, or detected by sonar or magnetic field anomalies. In all cases the search pattern should completely cover the search area without excessive redundancy or missed areas. Overlap is needed to compensate for inaccuracy and sensor error, and may be necessary to avoid gaps in some patterns.
  • Diver searches:
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  • **Spiral box search
  • **Compass grid search
  • **Ladder search
  • **Swim-line search
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  • *Searches using hand held submersible sonar transponders
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  • Searches by submersibles, remotely operated vehicles and autonomous underwater vehicles
  • Searches by surface vessels
  • Searches by aircraft
  • Searches from the shore

    Rigging and lifting

Most underwater rigging uses equipment and techniques common to rigging in other environments, except for the common use of buoyant lifting underwater, and the equipment designed and used specifically for that purpose.
  • Basic ropework, knots and splices, tackle
  • Rigging slings cargo nets and spreaders, lifting hooks and shackles
  • Lifting bags
  • Chain blocks, tirfors and pullers

    Inspection, measuring and recording

Use of basic hand tools

  • Hacksaws
  • Hammers
  • Cold chisels
  • Pliers
  • levers, wedges and crowbars
  • Screwdrivers and wrenches
  • Pipecutters and bolt cutters

    Underwater inspection

Inspection of underwater structures, installations, and sites is a common diving activity, applicable to planning, installation, and maintenance phases, but the required skills are often specific to the application. Much use is made of video and still photographic evidence, and live video to allow direction of the inspection work by the supervisor and topside specialists. Inspections may also involve surface preparation, often by cleaning, and non-destructive testing. Tactile inspection may be appropriate where visibility is poor.

Typed of underwater work and the related specialist occupations