Bill,

This is a simple system. The tube goes from the top of the transom down to the bottom of the inside of the hull. If water does not cover the end of the tube on the bottom of the hull, then the hull vents freely. When water covers the end of the tube, then pressure is allowed to increase until it reaches a point where water is pumped/pushed out the vent hole at the top of the transom. When the water no longer covers the end of the tube at the bottom of the hull, pressures will equalize. I think this would be excellent to evacuate the water inside the hull as long as the tube in the bottom of the hull is positioned where the water gathers while resting on the beach. I don't believe it to be particularly effective while sailing, as motion of the hull would periodically allow the low end of the tube to not be submerged and vent all pressure.