Riggin was born on May 2, 1906, in Newport, R.I. She learned to swim at age six in the Philippines while her father was stationed there with the United States Navy. She later joined the Women's Swimming Association of New York and trained under renowned coach Louis de B. Handley, winning several national contests as a member of the relay team. During her career she also captured four Amateur Athletic Union championships in springboard diving. Diving coaches did not exist at the time, but Handley tried to help Riggin and other divers one night per week.

Although women archers from the United States had performed in exhibitions at the Olympic Games in 1904, 1920 was the first year in which the United States sent women to the games as competitors in medal events. Many people considered it physically harmful for women to participate in athletics, and matters were further complicated when 14-year-old Riggin and other young females made the team. Officials wanted to replace the girls with older athletes but agreed to keep them on the Olympic team after protests were lodged.

At the 1920 Games in Antwerp, Belgium, Riggin won the first gold medal awarded to a woman for springboard diving and placed fifth in the platform event. The pool used for the competitions was part of the city moat and was filled with icy water. Many divers became disoriented as they tried to surface after a dive because the water was dark and murky.

Conditions were much better at the 1924 Olympic Games in Paris. Riggin received a silver medal in the springboard event and a bronze medal in the 100-meter backstroke.

Riggin turned professional in 1926 and performed in numerous exhibitions. She later managed a pool. During the 1930s, she appeared in some Busby Berkeley musicals. She also developed a career as a writer.

The International Swimming Hall of Fame inducted Riggin as a member in 1967. In 1986 at the age of 80, she won the 75-and-over division of a 1.5-mile (2.4-kilometer) race in Hawaii. She was chosen for the International Women's Sports Hall of Fame in 1988. Riggin died on Oct. 17, 2002, in Honolulu, Hawaii.