Some Basic Information about Underwater Propulsion Vehicles
An underwater propulsion vehicle, also known as underwater scooter or diver propulsion vehicle (DPV), is a diving equipment unit used by scuba and rebreather divers to increase their so-called range underwater.
Range is described under three conditions, and these are the limited amount of breathing gas that can be carried, the rate at which the breathing gas is used under efforts while diving, and the limited time imposed by dive tables to prevent decompression sickness among divers.
A DPV has its basic features of a watertight casing that is pressure-resistant that contains an electric motor being battery powered, that leads to driving a propeller. When the design was made for this vehicle, it was in such a way that the vehicle should not harm the diver, diving equipment, or marine life, and that it cannot be accidentally started nor will run away from the diver, and that the vehicle has to remain neutrally buoyant while it is used underwater.
DPVs are typically used in cave diving and technical diving where the vehicles serve as a help in moving bulky equipment and thus allowing the diver to make better use of the limited underwater time as stated by the decompression requirements for deep diving. DPV accessories, if mounted on the accessory board of the DPV can make the vehicle more useful underwater. Compasses, cameras, lobster sticks, and also spear guns are some of the accessories that can be mounted on to the DPV.
DPV also serves for military applications that include delivery of combat divers and their equipment over distances or at speeds that can be considered as not practicable.
The operation of DPV requires more than situational awareness than mere simple swimming since its operation requires simultaneous depth control, buoyancy adjustment, monitoring of breathing gas and navigation.
DPV is available in several kinds and the most common type is the one that tows the diver who holds onto the stern or bow. With the diver placed parallel to and above the propeller wash, this tow-behind scooter is at its most efficient operation.
Fish-shaped vehicles or manned torpedoes are another type of DPV and one or more divers can be sitting typically on top of the vehicle or in hollows inside.
Described as a submersible rigid-hulled inflatable boat, this another kind of DPV is called a subskimmer that is powered by a petrol engine if on the surface, and when submerged, the petrol engine is sealed, and the vehicle then runs on battery-electric thrusters that are located ona a cross-arm that is steerable.
Note that as DPVs get bigger, they are now merged into submarines. There are also small submarines called wet subs, where the pilot’s seat is flooded that then requires the diver to wear diving gear.
Cited reference: navigate to these guys