Surface-supplied diving

Surface-supplied diving is a mode of underwater diving using equipment supplied with breathing gas through a diver's umbilical from the surface, either from the shore or from a diving support vessel, sometimes indirectly via a diving bell. This is different from scuba diving, where the diver's breathing equipment is completely self-contained and there is no essential link to the surface. The primary advantages of conventional surface supplied diving are lower risk of drowning and considerably larger breathing gas supply than scuba, allowing longer working periods and safer decompression. It is also nearly impossible for the diver to get lost. Disadvantages are the absolute limitation on diver mobility imposed by the length of the umbilical, encumbrance by the umbilical, and high logistical and equipment costs compared with scuba. The disadvantages restrict use of this mode of diving to applications where the diver operates within a small area, which is common in commercial diving work.

The copper helmeted free-flow standard diving dress is the version which made commercial diving a viable occupation, and although still used in some regions, this heavy equipment has been superseded by lighter free-flow helmets, and to a large extent, lightweight demand helmets, band masks and full-face diving masks. Breathing gases used include air, heliox, nitrox and trimix.

Saturation diving is a mode of surface supplied diving in which the divers live under pressure in a saturation system or underwater habitat and are decompressed only at the end of a tour of duty.

Air-line, or hookah diving, and "compressor diving" are lower technology variants also using a breathing air supply from the surface.

There are two basic modes of surface-supplied diving, and several variations for supplying breathing gas to divers from the surface.

Surface oriented diving, with or without a stage or open bell, is where the diver starts and ends the dive at surface pressure. The diver is decompressed during the ascent or by surface decompression in a decompression chamber. It may also be referred to as bounce diving, an ambiguous term.

In addition to the standard system of surface-supplied diving using a diver's umbilical and diving helmet or full-face diving mask to provide the diver with compressed atmospheric air from a low-pressure diving compressor, there are other configurations in use for surface oriented diving:

Technically, atmospheric suit diving, scuba diving and freediving are also "surface oriented", but are not "surface-supplied".