A diving chamber has two main functions:

There are two basic types of submersible diving chamber differentiated by the way in which the pressure in the diving chamber is produced and controlled.

The historically older open diving chamber, open diving bell or wet bell is in effect a large diving bell, utilising an open bottom, the equivalent of a moon pool, to equalise internal air pressure and external water pressure automatically without the need, necessarily, to measure and control it. An air compressor or bottled compressed air is required to maintain the volume of the air as it becomes compressed with increasing depth, or to make up for oxygen depleted by the occupants' breathing and for carbon dioxide removed from exhaled air by a carbon dioxide scrubber system. This type of diving chamber can only be used underwater, as the internal air pressure is directly proportional to the depth underwater and raising or lowering the chamber is the only way to adjust the pressure.

A sealable diving chamber, closed bell or dry bell is a pressure vessel with hatches large enough for people to enter and exit, and a compressed breathing gas supply to raise the internal air pressure. Such chambers provide a supply of oxygen for the user, and are usually called hyperbaric chambers whether used underwater or at the water surface or on land to produce underwater pressures. However, some use submersible chamber to refer to those used underwater and hyperbaric chamber for those used out of water. There are two related terms which reflect particular usages rather than technically-different types: