RedactedNarrative: The operator of unit #1, was attempting to start his personal watercraft while drifting down the river from the boat ramp.  The operator of unit #1 was not wearing a personal flotation device, and did not have one on board.  On the 4th or 5th attempt to start the pwc, it exploded and caught on fire.  The explosion ejected the operator approximately 4 feet up, and back into the air.  The operator landed in the river and was able to swim to shore and call for help.  The Oregon fire dept. responded and extinguished the fire and towed the back half of the PWC back to the ramp.  The front half and engine sunk to the bottom of the river.  The operator was not injured and refused treatment from Oregon fire and rescue. The faulty equipment was caused from a faulty ignition and/or a battery that did not have its terminals protected from producing an arc. 