Women were first allowed to compete in Olympic swimming events in the 1912 Summer Games in Stockholm. Twenty-seven female swimmers from eight nations participated. The Australian swimmer Fanny Durack, in the 100-meter freestyle, won the first gold medal in a women’s Olympic swimming event. The 1912 Summer Olympics are also notable for being the first Games in which electric timing devices were used.

In 1922, the German-American swimmer Johnny Weissmuller became the first person to swim 100 meters in under one minute, using the Australian crawl. Weissmuller, in his 10-year swimming career, won five Olympic gold medals, 52 U.S. National Championships and set 67 world records. His worldwide popularity helped spur interest in swimming as a competitive sport and recreational activity, and the 1920s are regarded as a “golden age” for the sport of swimming. Also in 1922, the American swimmer Sybil Bauer, competing in the 440-meter backstroke, became the first woman to break a men’s world record.

For swimming events at the 1924 Summer Olympics in Paris, pool-lane dividers made of cork were introduced, as well as lines on the bottom of the pool to help orient swimmers.

New York-born Gertrude Ederle became the first female swimmer to complete the 35-mile swim across the English Channel in August 1926. Her swim began at a cape in northern France and ended 14 and a half hours later on the southeast shores of England. Her record held until 1950, when American swimmer Florence Chadwick traversed the Channel from France to England in 13 hours and 20 minutes. The following year, Chadwick crossed the Channel again, from England to France, making her the first female to swim across the Channel in both directions.

In the late 1920s the competitive swimming community began the scientific study of swimming to improve technique. University of Iowa coach David Armbruster devised the underwater observation window and began filming swimmers underwater. The Japanese also used underwater filming to study the mechanics of swimming strokes, and Japanese swimmers excelled at the 1932 Summer Olympics in Los Angeles, winning 12 swimming medals, the most of any country.