By the mid twentieth century, two basic systems for scuba (self-contained underwater breathing apparatus) had emerged: open-circuit scuba where the diver's exhaled breath is vented directly into the water, and closed-circuit scuba where the carbon dioxide is removed from the diver's exhaled breath which has oxygen added and is recirculated.
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Scuba
Scuba diving is a mode of underwater diving in which the scuba diver uses a self-contained underwater breathing apparatus (scuba) which is completely independent of surface supply, to breathe underwater.
