long journey no gain at last ship problem is reached. buoyancy (pronounced /ˈbɔɪ.ənsi/) is the upward force that keeps things afloat. The net upward buoyancy force is assumed equal to the magnitude of the weight of fluid displaced by the body. This force couldn't make ship maker stop design tank ship, container ship and cruise ship. Water spin effect is a kind of Triboelectric effect which might reduce gravity.