A rebreather is an apparatus also known as a Closed Circuit Underwater Breathing Apparatus, or CCUBA. This device scrubs or removes carbon dioxide from a diver's exhaled breath; a small amount of oxygen or an oxygen-gas mixture is added to the remaining breath to allow for a longer dive with less reserve oxygen and smaller tanks. There are many fewer bubbles emitted from a diver using a rebreather as compared to a one using traditional diving equipment. The oxygen in the escaping bubbles is filtered through the rebreather and used by the diver's body instead of being wasted in the water. By utilizing a rebreather, the diver is able to remain at depth much longer than with traditional diving tanks.
There are many advantages to using a rebreather as compared to traditional tanks, both to the diver and the underwater surroundings. By producing fewer bubbles, the diver is able to maintain a much stealthier position in the water, making the rebreather a very good military or tactical device. By inhaling the scrubbed gases through the rebreather, the breathing mixture is much warmer and more pleasant on extended duration dives, which makes the dive less physically demanding. Divers also suffer fewer effects of the bends when using a rebreather, making this a safer method of diving and ascending from the depths.
When using traditional diving gear, divers exploring dangerous shipwrecks are subject to the emitted bubbles disturbing objects within the wreck. The bubbles have the power to ignite unexploded armaments from sunken warships and can disturb dirt and silt, making vision and escape from the inner clutches of a wreck difficult. More dangerous than this, however, is the tendency for the diver's exhaled oxygen to be trapped in the inner compartments and form large air pockets. This trapped oxygenated air aids in the formation of rust and deterioration of the wreck.
Divers require specialized training in the use of a rebreather, and the feel of breathing the scrubbed gas requires some getting used to. In the event of two or more divers encountering a problem at depth, the ability to simply switch back and forth with the other's oxygen hose is not possible. This single factor convinces many divers to forgo the technology and remain equipped with the traditional diving equipment. This breathing apparatus has been tested at height by mountain climbers with little success. The equipment has not yet been designed to withstand extremely cold conditions.