A diving bell, also known as a wet bell, is an airtight chamber used for transporting divers underwater. It is open on the bottom, and suspended on a cable. The diving bell was the first type of diving chamber, and its use was first described in the fourth century BCE by Aristotle. The modern diving bell was designed in 1535 by Guglielmo de Lorena.
The diving bell works by being lowered straight down into the water, so that its interior remains full of air. The same principle can be observed by lowering an empty cup upside down into a larger container full of water. If a piece of paper is placed in the top of the cup before lowering it into the water, it will remain dry as long as the top of the cup is pushed straight down into the water.
Diving bells are weighted to ensure that the bottom remains level as it is lowered, and they are built heavy enough to sink even when filled with air. In addition, extra breathing air is pumped into the diving bell via tubes in the top. This helps maintain consistent air pressure within the bell, preventing water from entering, and ensuring that the air remains oxygenated.
Diving bells are raised and lowered by a cable from a crane on a ship or dock. It does not have any independent means of moving. In addition to being used as transport for divers, diving bells are also used in underwater rescue. They are typically large enough to accommodate a few people.
The concept behind the diving bell is also used in diving gear and underwater habitats. The standard diving helmet works the same way as the diving bell, allowing the inside to stay dry. The moon pool, on the other hand, is a large submersible chamber, the size of a room or two, based on the principles of the diving bell.
Moon pools are used for offshore oil drilling, for underwater exploration and research, and as an underwater habitat. In underwater habitats, moon pools are anchored to the ocean floor. Therefore, they are not mobile, but can be used for much longer periods of time than diving bells. Moon pools provide dry space in which divers and other underwater workers can become accustomed to the increased pressure of the underwater environment. The eliminated need to return to the surface helps prevent decompression sickness, or the bends, associated with ascending too quickly from deep ocean.