diver propulsion vehicle; underwater scooter
A small motorized device that divers hold onto to move through water without swimming. Often used in recreational diving.
I used an underwater scooter on the diving tour.
With a DPV, you can easily explore a wide area.
Compound of 水中 (underwater) and スクーター (scooter), a straightforward loanword adaptation describing a device that 'scoots' through water.