RedactedNarrative: 4 occupants fishing on vessel, all were staged off the aft end of the vessel. The weight of the occupants dipped the transom drain holes underwater and the drain holes started back flowing water into the transom. 
  
  the pie plate that allowed access to the hull via the transom was missing or unsecured (not located upon inspection). The back flowing water drained into the hull. 
  
  per captain the vessels bilge pumps were inoperative. by the time an issue was noticed by the occupants the vessel was over flowing and was sinking with no way to de-water. all occupants donned pfd's and exited the vessel as it sunk then capsized. no injuries reported, vessel was recovered by Seatow.