moon pool

moon pool (MOON POOL) - n., an opening in a ship's hull or marine oil rig that provides access to the sea for drilling and other equipment.


Where obviously the hull around it is sealed, so that the boat still floats. Can also be used in underwater habitats, though there the water must be kept out by air pressure. Wikipedia has a little more if you're curious. So called because, on some nights, moonlight can be seen reflected by the surface of the sea through the opening, making it resemble a swimming pool.

---L.