A diver propulsion vehicle (DPV, also known as an underwater propulsion vehicle or underwater scooter) is an item of diving equipment used by scuba and rebreather divers to increase range underwater. Range is restricted by the amount of breathing gas that can be carried, the rate at which that breathing gas is consumed under exertion, and the time limits imposed by the dive tables to avoid decompression sickness. DPVs can have military application; an example is the Diver Propulsion Device (DPD) from STIDD Systems in the US.
A DPV usually consists of a battery-powered electric motor, which drives a propeller. The design must ensure that: the propeller is caged so that it cannot harm the diver, diving equipment or marine life; the vehicle cannot be accidentally started or run away from the diver; and it remains neutrally buoyant under all conditions.
DPVs are useful for long journeys at constant depth where navigation is easy. Typical uses include cave diving and technical diving where the vehicles help move bulky equipment and make better use of the limited underwater time imposed by the decompression requirements of deep diving.
For many recreational divers DPVs are not useful. Buoyancy control is vital for diver safety: The DPV has the potential to make buoyancy control difficult and cause barotrauma if the diver ascends or descends under power. Visibility of less than 5 meters makes navigating a DPV difficult. Also, many forms of smaller marine life are very well camouflaged or hide well and are only seen by divers who move very slowly and are very vigilant.
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