Not sure if a player triggered this as a glitch, but the other day I located a vehicle on the shore of the Prison Island. Weird, since the island is only a half a kilo long and trucks are not needed, but the weirdest part was that it was floating on the ocean water, about 20 meters deep right next to the docks facing the opposite shore.
As soon as I investigated it and touched the vehicle, it sunk to the bottom of the ocean.