RedactedNarrative: On May 25, 2014 at approximately 15:30, I was dispatched to a vessel fire located just out from TVA Dam Free Launch Boat Ramp on Douglas Lake.  Upon arrival I noticed the vessel TN 8755 AR drifting between the boat ramp and no wake buoy completely engulfed in flames. All persons on board had escaped from the vessel uninjured.  They were picked up and taken back to shore by two unidentified vessels whom left the scene before our arrival.  
  
  According to interview/statements; after launching the vessel, subject was idling approximately 75 yards away from the boat ramp when the youngest female ran from the back of vessel stating she smelled a strong odor of gasoline.  Operator shifted the vessel into neutral, heard a loud pop, and then an explosion.  Operator attempted to use the fire extinguisher aboard the vessel to extinguish the flame, but it was too intense.  
  
  Occupant1 stated that when Occupant2 reached the front of the vessel that her hair was smoking, so she picked her up and threw her into the lake.  All of the occupants in the vessel had singed eyelashes and hair on the front of their heads.  Operator had just purchased the vessel on May 15, 2014 and stated that all of the vessels electronic systems were functioning.  Operator also stated that they had stopped prior to reaching the lake and purchased $50.00 worth of fuel for the vessel, but he didn’t vent the fumes before launching the vessel.  The vessel burned completely and sank to bottom of Douglas Lake at approximately 16:34.  The fuel cell was the only thing salvaged from the vessel.  This incident occurred in Sevier County Tennessee.