US Patent 9132897 Boat lift

A boat lift having a plurality of flotation tanks positioned under each of opposite sides of a frame of the boat lift. Trunk lines receive water through a port near the rear of the trunk lines, and communicate water into a plurality of flotation tanks. Water flow is regulated so that the plurality of the tanks fill relatively evenly to maintain a surface of the boat lift that is generally horizontal at all times. Hingeable connection of the dock to a bulkhead, along with lateral stabilization, participate in maintaining a generally horizontal attitude for the boat lift. Water is expelled from the plurality of flotation tanks by pumping water from the flotation tanks, allowing the frame of the boat lift to rise.