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.
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.
Pilotage involves navigation by naturally observable landmarks and phenomena, such as sunlight, water movement, bottom composition (for example, sand ripples run parallel to the direction of the wave front, which tends to run parallel to the shore), bottom contour and noise. Although natural navigation is taught on courses, developing the skills is generally more a matter of experience.[1]
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 (one complete upward and downward sweep of a kick), 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 animpeller log, to pacing off the distance along the bottom with the arms.[2]
Use of aguide line orjackstay. Aguide 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. Ajackstay serves the same purpose in heavy duty format.
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 bysonar ormagnetic 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.[4][5]
Mostunderwater 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.
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.[6][7][8]
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Typed of underwater work and the related specialist occupations
^UK Divers (October 16, 2007)."Underwater Navigation".UKDivers.net. Archived fromthe original on 13 March 2016. Retrieved16 May 2016.Navigation by reference to terrain features, both natural and artificial, usually with the aid of an appropriate chart.
^Scully, Reg (April 2013). "Topic 7: Underwater Navigation".CMAS-ISA Three Star Diver Theoretical Manual (1st ed.). Pretoria: CMAS-Instructors South Africa.ISBN978-0-620-57025-1.
^"2: Underwater Search and Recovery Techniques".U.S. Navy Salvage Manual(PDF). Vol. 4: Deep Ocean Operations S0300-A6-MAN-040 0910-LP-252-3200. United States. Navy Department. Supervisor of Salvage and Diving. 1 August 1993.Archived(PDF) from the original on 5 April 2023. Retrieved11 April 2023.
^Hanekom, Paul; Truter, Pieter (February 2007). "Section 17: Seabed searches".Diver Training Handbook (3rd ed.). Cape Town, South Africa: Research Diving Unit, University of Cape Town.
^Bayliss, Mel; Short, David; Bax, Mary (17 March 1988).Underwater Inspection. Taylor and Francis. p. 229.ISBN9780419135401.
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