Abstract: A boat has enclosed flotation within a closed bilge or floor of the boat, which is internally raised so that the interior floor of the vessel is slightly above the normal operating water line level of the vessel. The boat has bilge drain valves of a size considerably increased over the one or two square inch drains typified in the prior art. The size of these drain valves is such that, when opened, they represent a significant portion of the transom area being opened to the sea. Spring closure or manual actuation of the valve prevents the ready passage of water into the interior of the boat during heavy waves, especially during following seas which might tend to trigger a flapper operated drain valve. In combination this provides a boat that, if swamped will, even when fully loaded, have sufficient buoyancy to raise itself so that no portion of the bilge is below the water line and with the oversized valves open will have sufficient flow rate that it will rise faster than it can be reswamped.