Synchronized swimming, also known as pattern swimming or water ballet, is an Olympic sport that mixes swimming with ballet and gymnastics, and includes diving, stunts, lifts, and endurance movements. Synchronized swimming started as an organized sport at the beginning of the 20th century, when Margaret Sellers, a Canadian water polo player, developed the art of 'ornamental swimming'. The term synchronized swimming was coined later on by former gymnast Katherine Curtis to refer to her group of swimmers, later renamed The Modern Mermaids. In the 1940s and '50s, Esther Williams became a Hollywood sensation by performing synchronized swimming routines in a series of films.

Women's synchronized swimming didn't become an Olympic sport until 1984, when both duets and teams of four to eight swimmers were allowed to compete. The sport is now ruled by the Federation Internationale de Natation Amateur or FINA. The US team holds world records for receiving a perfect score of ten 10s and for winning the most medals. Synchronized swimming has been the most successful American Olympic sport since its inception, as the US team has won gold or silver medals in each event.

Requirements of synchronized swimming include wearing a noseclip and a hair bun, which is kept in place with unflavored Knox gelatin. Competition suits and costumes are usually handmade to fit a special theme or music score. While these items don't count directly towards the score, they do affect the overall artistic impression of the performance.

Technical merit is evaluated based on a series of predetermined elements, such as execution of strokes and transitions, difficulty, and synchronization. Arm sections and figures, similar to those of figure skating, are also required, and all elements must be presented in a specific order. Points are deducted for touching the bottom of the pool, lack of fluidity, and missing required elements.

Free routines are also an important part of synchronized swimming. They give swimmers the opportunity to demonstrate artistry, choreography, and musical interpretation. In preliminary competitions, free routines account for up to 65% of the total score.

Synchronized swimming routines can last from two and a half to five minutes depending on technical requirements and the number of swimmers. Solos are usually under three minutes, while large teams make use of longer routines to include all required technical elements. Because synchronized swimming routines require exceptional breath control, judges also take into consideration the ability of the swimmers to preserve the illusion of effortlessness while holding their breath for up to two minutes.