Scuba diving ("SCUBA" originally being an acronym for self contained underwater breathing apparatus, now widely considered a word in its own right) is a form of underwater diving in which a diver uses a scuba set to breathe underwater.

Unlike early diving, which relied either on breath-hold or on air pumped from the surface, scuba divers carry their own source of breathing gas (usually compressed air), allowing them greater freedom of movement than with an air line. Both surface supplied and scuba diving allow divers to stay underwater significantly longer than with breath-holding techniques as used in snorkelling and free-diving. Depending on the purpose of the dive, a diver usually moves underwater by swimfins attached to the feet, but external propulsion can come from an underwater vehicle, or a sled pulled from the surface.

The first commercially successful scuba sets were the Aqualung open-circuit units developed by Emile Gagnan and Jacques-Yves Cousteau, in which compressed gas (usually air) is inhaled from a tank and then exhaled into the water adjacent to the tank. However, the scuba regulators of today trace their origins to Australia, where Ted Eldred developed the first mouth piece regulator, known as the Porpoise. This regulator was developed because patents protected the Aqualung's double hose design. It separated the cylinder from the demand valve giving the diver air at the same pressure surrounding his mouth, not surrounding the tank.

Tanya Streeter (b. Tanya Dailey, 10 January 1973 in Grand Cayman) is a British/Caymanian world champion free-diver, inducted into the Women Diver's Hall of Fame in March 2000. For over two months from 17 August 2002 she held the overall "no limits" freediving record (greater than the mens record) with a depth of 525 feet (160 m), which is still the women's world record for No Limits Apnea.

Streeter was born to Jim and Sandra Dailey in the Cayman Islands. She has two sisters and a brother. She was educated in England at the independent girls' school Roedean and at Brighton University. She met and married her husband Paul Streeter in England. They moved to the Cayman Islands in 1995. They have a daughter Tilly Annina Andrus Streeter (b. 19 August 2008). After giving birth Tanya Streeter officially retired from freediving. She currently resides in Austin, Texas.

Streeter took up freediving at age 25 and almost immediately began to break records. She made her first important breakthrough in 1998 when she bettered Deborah Andollo's Women's No Limits diving record by 10 feet, achieving a total depth of 370 feet (113 m). She was inducted into the Women Diver's Hall of Fame in March 2000. In 2002, she broke the men's No Limit (NLT) world diving record by diving to a depth of 525 feet (160 m) near the Turks and Caicos Islands, a record which was surpassed later that year by French diver Loïc Leferme (162 m). 19 July 2003 she broke the men's Variable Weight (VWT) world record by diving to a depth of 400 feet (122 m) and held it over a year until the record was broken by Carlos Coste (135 m) in Puerto la Cruz, Venezuela on 27 October 2004, but as a women's record it lasted almost seven years, until Natalia Molchanova reached 125 m in June 2010 in Kalamata, Greece.