Answer: scupper

AnswerCrossword Clue
SCUPPERDeliberately sink
SCUPPERNautical drain
SCUPPERDrainage opening in a ship's side.
SCUPPERDeck opening
scupperAn outlet in the side of a building for draining water
scupperto prevent from happening or succeeding; ruin; wreck.
scupperA hole in a ship's side to carry water overboard from the deck
scupperto ambush (to attack from a concealed place)