Abstract: A submersible unit comprises a portable, open or closed bottomed pneumatic chamber mounted on flexible drive tracks controlled by personnel from the chamber for operation along the bottom of a body of water, on the surface, at intermediate levels, in the air and on land. A safety chamber, connected to the submersible unit by an extendable linkage, can limit the depth of submergence of the submersible unit, stores cargo and carries power. Flooded compartments in the submersible unit and the safety chamber are supplied with compressed air to control the supported load and depth of submergence. Various accessories carried by the underwater unit enable the performance of a number of different on and under the water and land based tasks. A special pneumatic circuit enables equipment and propulsion to be controlled by touch control panels. A majority of operations are contained within the machine to minimize contamination of surrounding areas.