Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving. It is much used for sport diving and some sorts of work diving. The word SCUBA was originally an acronym for Self-Contained Underwater Breathing Apparatus. These initials originated in 1939 in the United States Navy to refer to their military diver''s rebreather sets. As with radar, the acronym has become so familiar that it is often not capitalized and is treated as an ordinary noun; for example, it has been taken into the Welsh language as "sgwba".