What is Underwater Propulsion?
In order to increase the range underwater of scuba and rebreather divers, they use an item of diving equipment called underwater propulsion vehicle, also known as underwater scooter or diver propulsion vehicle or DPV.
The meaning of range can be explained in three situations, and these are the restricted quantity of breathing gas that can be carried, the rate of breathing gas consumed under exertion, and the time limits stated by the dive tables in order to avoid decompression sickness of divers.
A DPV has some basic components which are a pressure-resistant watertight casing containing an electric motor that is battery-powered, and this drives a component which is the 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.
The usual uses of underwater propulsion vehicle are for cave diving and technical diving, where deep diving needs the help to move big equipment and making divers use better of the limited underwater time based on the decompression requirements. DPV accessories, if mounted on the accessory board of the DPV can make the vehicle more useful underwater. The accessories that can be mounted on to the DPV are compasses, cameras, lobster sticks and even spear guns.
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.
Know that the use of DPV is more than simple swimming, but requires depth control, buoyancy adjustment, monitoring of breathing gas, and navigation.
There are several types of DPV, and the most common type is that which tows the diver while holding onto the handles on the stern or bow. The diver of this tow-behind scooter is placed parallel to and above the propeller wash and this makes the vehicle most efficient.
Another type of DPV is called manned torpedoes which are fish-shaped vehicles where one or more divers can sit astride or in hollows inside.
There is another type of DPV which is submersible and thus called the subskimmer described as a submersible rigid-hulled inflatable boat, which if on the surface is powered by a petrol engine, and when submerged, the petrol engine is sealed, and thus the vehicle runs on battery-electric thrusters that are mounted on a cross-arm that is steerable.
As DPVs get bigger, they now turn into the big vehicle called the submarines. There is a wet sub, which is a small submarine, where the seat of the pilot is flooded and thus the diver is to wear a diving gear.