Divers that are members of professional or commercial diving organisations are very aware of the differences between offshore and onshore diving, but the amateur diver may not appreciate the distinct requirements of each situation. An understanding of what is needed for each environment is crucial for both the safety and the enjoyment aspects of diving.
As the name indicates, this is diving that takes place in oceans, gulfs and seas. Support tends to be supplied from the surface, usually from boats or stationary platforms. The type of suit worn by the diver will vary depending on location; warm water divers often choose a wetsuit, while those in cold or dangerous regions will wear a drysuit or other protective gear. Divers need to be more meticulous when cleaning equipment, taking care to remove corrosive salt water each time the gear encounters water.
The need for a large workforce means that offshore work is often the entry point to commercial diving for the newly certified. The oil and gas industries use divers to inspect and maintain the underwater structures involved in removing oil from beneath the seabed. The difficulty in getting to oil platforms often means that divers will be working for several days or weeks at a time, enduring long shifts and rapidly changing weather. The difficult and dangerous work conditions combined with the inexperience of the divers have made offshore diving the most hazardous employment for professional divers.
Perhaps more accurately called inland diving, this takes place in rivers and lakes, often near dams, bridges and pontoons. Support for these divers can be surface or SCUBA depending on the location and depth of the dive. Suits are wet- or dry- depending on the water. The freshwater conditions that prevail in onshore diving mean less corrosion to diving gear, although equipment still must be carefully checked before and after each dive.
Unlike offshore employment, most commercial divers involved in freshwater work are supporting civil engineering projects. Bridge structures and dams must be routinely checked for integrity, meaning divers may be working in a current or other difficult environment; however, the nearness to land allows onshore divers to work shorter days and avoid the weeks of continual work.
Scientific diving undertaken by research can be both on- and offshore and normally takes place in shallow waters. Divers can be surface supported or use SCUBA equipment depending on the situation and a scientific diver is likely to identify himself as a scientist first and a diver second.
Underwater photography is done by divers, again in both on- and offshore situations. Highly trained commercial divers may be employed to operate cameras for feature films, documentaries and wildlife studies.
Amateur divers that are hoping to purse a commercial diving profession have a wide variety of situations to consider. Those with special skills such as camera operation or a marine biology background can consider unique jobs while those divers just beginning a career are somewhat more limited in their options.