The non-certificated pilot took off with one passenger on board and with both doors removed. Witnesses observed the pilot make a number of passes near boats, under power lines, and near people on the surface. A number of witnesses stated the passenger was sitting with his legs hanging out the passenger's doorway. During one of the passes, the aircraft hit the front end of a boat. The passenger in the aircraft and two occupants on the boat were fatally injured. The pilot and one occupant on the boat were seriously injured. An investigation revealed the pilot had been flying regularly, he had about 313 hours total flying time, but had no medical or pilot certificate. No authorization had been obtained to fly the aircraft without doors. The pilot reported adding 12 gallons of auto fuel before takeoff. The plane had flown about 3.5 hours before crashing. Due to impact damage and being submerged in water, the amount of fuel on board at impact was not determined. The pilot's blood/alcohol level was reported as .14%.