A moon pool is an opening that is located in the hull of a sailing vessel that permits easier and safer access to the water. It permits sailors, divers and researches to reach the water easily, and allows those in the oil drilling business to safely bring tools and instruments into the water. This opening makes it easier to enter the water, especially when there is ice on the water or when the sea is rough.
This specially engineered pool originated in the oil drilling business and is commonly found on marine drilling platforms or drill ships. A moon pool can also be located on marine or underwater research ships, as well as underwater habitats. There are four different types of moon pools that are used.
The first type of moon pool is an above water style and is located inside a chamber in the vessel that is above sea level. With this type of pool, there is open air found above and below the chamber. The chamber is easily accessed through open hallways and stairways. This type is most commonly found on oil drilling platforms.
The second style is the at water level style where the hull of the ship is below sea level but the opening is located right at the water level. This will make it look like there is a swimming pool in the hull of the vessel. The sides of the moon pool are built up to a height that is well above sea level to prevent the ship from sinking. Doors found near the hull will allow for the opening to be sealed shut while the ship is moving, or if it encounters stormy weather.
The third type is the below the water level style where the opening, just as the name suggests, is found below the water level. The only way this style of pool can be built in order to prevent the ship from sinking is if the chamber which houses the moon pool is airtight. This means that the chamber will not be exposed to the air at all. To gain access to this chamber the person entering will have to go through an airtight door.
The final style is the underwater habitat; in which the entire pool is under the water in a uniquely designed underwater habitat, similar to the diving bell. This can provide divers and researches a dry underwater place to go. They will be able to work and rest without the need to climb their way to the surface of the water. These habitats are connected to the bottom of the sea and the opening of the pool is the only entrance or exit into the chamber.