Swimming was still a risky activity at the first modern Games in Athens in 1896. For the 1,200m freestyle event, a boat deposited competitors in the icy waters of the Mediterranean the required distance from the shore. Winner Alfred Hajos later confessed that the will to live had been a bigger motivation than the will to win.

Men and women now compete in 16 events, involving four different strokes across a range of distances. Freestyle races cover 50m, 100m, 200m, 400m, 800m, 1,500m, 10,000m; the 800m is for women only and the 1,500m for men only. The butterfly, backstroke and breaststroke races each cover 100m and 200m. All four strokes are used in the 200m and 400m individual medley events. The 4 x 100m freestyle, 4 x 200m freestyle and 4 x 100m medley relays complete the programme.

Each race has a maximum of eight swimmers. Preliminary heats in the 50m, 100m and 200m lead to semi-finals and finals based on the fastest times. In relays and individual events of 400m or more, the eight fastest finishers in the preliminaries advance directly to the finals.

These are judged events. In diving, competitors perform a series of dives and are awarded points up to 10 depending upon their elegance and skill. Points are adjusted for the degree of difficulty, based on the number and types of manoeuvres attempted, such as somersaults, pikes, tucks and twists. The judging for synchronised swimming resembles that for figure skating, with judges awarding marks out of a possible 10 for artistic impression and technical merit.

In water polo, 12 teams qualify for the men's division at the Olympic Games while eight compete in the women's. Teams play each other in round-robin groups, with the top four from each pool going into the quarter finals in the men’s competition, and the top two from each pool going into a pair of semi-finals in the women’s competition.