Why Do Submarines Sink and Rise?

More fun facts

• An object sinks when the upward push of the water, called upthrust, is smaller than its weight.
• If something is denser than water, it can never push aside enough water to hold itself up.
• Submarines use compressed air, squeezed and stored under pressure, to push water out of their tanks.
• You can make a straw submarine in a plastic bottle: squeeze the bottle and it sinks, let go and it rises.
• In 1904 the U.S. Congress approved four new, bigger submarines.
• Some early Holland-type submarines were 63 feet 10 inches long.
• Many deep-sea animals act a bit like submarines. They rise toward the surface each evening to feed and sink back into the dark when the sun comes up.

Sources: BBC, BBC, Scientific American, NOAA