A flood vent for mounting in a building structure subject to flooding includes a frame and a buoyant door. The frame has an external surface configured to be inserted into an opening in the building structure and has an upper wall and a lower wall longitudinally displaced from the upper wall and a pair of displaced sidewalls extending between the upper wall and lower wall on respective ends thereof. The buoyant door is pivotally mounted between the sidewalls proximate the upper wall of the frame. The door is mounted to be longitudinally movable a float distance between a first position and a second position, closer to the upper wall than the first position. When the door is in the first position it is not substantially rotatable and when the door is in the second position it is free to pivot.