Scuba diving: underwater breathing, equipment, and safety

Equipment and basic characteristics

Modern scuba gear typically includes a cylinder of compressed gas, a demand regulator that delivers breathable gas at ambient pressure, a buoyancy control device to adjust ascent and descent, and a mask and fins for vision and propulsion. Exposure protection such as wetsuits or drysuits helps maintain body heat. Common accessories are dive computers, depth gauges, and knives.

• Tanks: made of steel or aluminum; divers choose based on durability, buoyancy, and capacity — see steel or aluminum tanks.
• Regulator: reduces cylinder pressure to ambient and provides air on demand.
• Buoyancy control device (BCD): enables neutral buoyancy and controlled ascents/descents.
• Instruments: dive computers and gauges monitor depth, time, and remaining gas.

History and development

The development of modern scuba equipment accelerated in the 20th century. Early breathing systems and surface-supplied gear evolved into self-contained systems when inventors combined compressed-gas cylinders with demand regulators. The modern open-circuit scuba regulator, which supplies gas only when the diver inhales, made recreational and professional diving more practical and safer.

Safety, training and physiological limits

Scuba diving carries risks that are managed through training, planning, and conservative procedures. Key medical concerns include decompression sickness from rapid ascent, nitrogen narcosis at depth, and oxygen toxicity with high oxygen partial pressures. Certification agencies and training courses teach dive planning, emergency procedures, gas management, and ascent rate limits. Many divers use dive tables or dive computers to reduce decompression risk.

Uses and importance

People dive for recreation, scientific research, underwater photography, commercial and construction work, search and recovery, and military operations. Recreational diving is popular for exploring coral reefs, wrecks, and marine life; professional diving supports underwater engineering, archaeology, and resource extraction.

Distinctions and notable facts

Scuba should be distinguished from freediving (breath-hold) and from surface-supplied commercial diving. There are variations within scuba itself: open-circuit systems vent exhaled gas to the water, while rebreathers recycle and scrub carbon dioxide, extending gas use and reducing bubble output. Technical diving uses mixed gases and specialized equipment to reach greater depths or longer bottom times, demanding advanced training and planning. For more on terminology and the origin of the word, see acronym history, underwater breathing concepts, and breathing apparatus.