Scuba diving

Scuba diving is a mode of underwater diving that uses specialized breathing equipment. This equipment is completely independent of a surface breathing gas supply. The term SCUBA is an acronym for "Self-Contained Underwater Breathing Apparatus."

This independence allows divers to move more freely than surface-supplied divers. It also provides more time underwater than freedivers, who hold their breath. Divers use this skill for recreation, scientific research, military operations, and public safety.

Most divers use an open-circuit scuba system to breathe. In this system, one or more high-pressure cylinders contain breathing gas. A device called a diving regulator supplies this gas to the diver at ambient pressure. When the diver exhales, the gas is discharged directly into the environment.

Some divers use closed-circuit or semi-closed circuit rebreather systems instead. These systems recycle exhaled gases rather than venting them. This recycling process reduces the volume of gas used. Consequently, rebreathers allow for much longer dive durations for the same amount of gas.

Rebreathers offer several distinct advantages for specific types of divers. Because they produce fewer bubbles and less noise, they are ideal for covert military divers. They also help scientific divers avoid disturbing marine animals. Media divers use them to prevent bubbles from interfering with filming.

However, oxygen rebreathers are limited by depth. Using high percentages of oxygen at great depths creates a risk of oxygen toxicity. This condition can cause convulsions in the diver.

The history of scuba technology began in the 19th century. In 1878, engineer Henry Fleuss built the first commercially practical rebreather.

His apparatus used a rubber mask and a breathing bag. It supplied 50% to 60% oxygen from a copper tank. He used a bundle of rope yarn soaked in caustic potash to scrub carbon dioxide.

Later, in 1942, Jacques-Yves Cousteau and Émile Gagnan designed the Aqua-Lung. This was a successful open-circuit system using a demand regulator and high-pressure tanks.

They patented the system in 1945, which changed underwater exploration forever.

Modern divers rely on a wide variety of equipment to manage their environment. Divers wear fins on their feet to move through the water.

They may also use a diver propulsion vehicle or a towed sled for extra speed. A mask is required to improve underwater vision.

To manage buoyancy, divers use weights to overcome natural buoyancy. They also use buoyancy control devices, such as a stabilizer jacket or a buoyancy compensator.

A dive computer is often used to monitor decompression status.

This helps ensure the diver ascends safely.

Advanced divers often use specialized configurations to handle difficult environments. Sidemount diving involves mounting cylinders alongside the diver's body rather than on the back.

This setup is popular for cave diving because it helps divers pass through tight spaces. It also provides easy access to cylinder valves and gas redundancy. Some technical divers use a backplate and wing configuration. This places a buoyancy bladder behind the diver.

This arrangement is useful for carrying multiple extra cylinders during long or deep dives.

Technical diving involves activities that exceed standard recreational limits. These dives may expose divers to higher risks of injury or death. To manage these risks, divers often use alternative gas blends like nitrox. Nitrox is an oxygen-enriched air mixture.

The use of nitrox was documented by the U.S. Navy in the 1950s. It was later used for scientific purposes by NOAA in 1970. Eventually, training agencies like NAUI and PADI began supporting nitrox for recreational use. Using these mixtures can help reduce the time a diver spends on decompression.