RedactedNarrative: Operator & passenger fell off V1 and the PWC was upside down for about 10 minutes before righted. Operator & passenger righted the machine and climbed aboard. tried to start yet wouldn't so tried 3 more times to start & didn't. Opened up the engine compartment to see if any water was inside & it was empty.  Let the machine set for about 3 minutes and then tried to start it & it exploded.  The explosion sent the operator, Injured#1 15-20 feet in the air. The passenger, Injured#2 was knocked unconscious.  The PWC split along the rivet seam on the entire starboard side and entire stern.  There was much engine damage.  Both individuals were wearing life jackets.