Upon receiving instructions from the guides on how to operate the vessel, unit 1 accelerated in the vicinity of the dock and other vessels in Broad Creek @ Palmetto Bay Marina. After accelerating, unit 1 collided with unit 2 causing the three occupants of unit 2 to fall in the water. unit1 ignored instructions to stop and collided with another vessel at the marina. The operator of unit 1 was removed from the vessel along with her passenger. The occupants of unit 2 were rescued and returned to the dock.