Swimming has featured in every edition of the Games since 1896. Originally limited to freestyle (crawl) and breaststroke events, the backstroke was added in 1904.

At the first three modern Olympic Games, swimming took place in open water - in seas, rivers and lakes. A pool was used for the first time at the London 1908 Games, when the rules were finally standardised.

In the 1940s, breaststrokers discovered they could go much faster by bringing both arms overhead together. This was soon banned in the breaststroke, but became the butterfly stroke, which is now the fourth stroke used in competitive swimming

There are two types of swimming competitions: long course and short course. Long course is held in a 50m pool and short course is held in a 25m pool. The Olympics is always held in a 50m pool but there are international competitions in both long course and short course.

There are a range of events in the swimming programme. Typically these will be 50m, 100m and 200m races in each of the strokes (breaststroke, backstroke, butterfly and freestyle). In addition, there will be longer freestyle events : the 400m, the 800m (for women), and the 1500m (for men).

There are also 200m and 400m individual medley races for both men and women, where they will complete lengths using breaststroke, backstroke, butterfly and freestyle strokes.  Finally, there are male and female relays swum over 4 x 50m.

Along with the instantly recognisable world record holder and gold medal winner Rebecca Adlington, Britain can boast a range of successful swimmers. Find out more about Britain's hopefuls with British Swimming.

Fédération Internationale de Natation (FINA) is the International Federation recognised by the International Olympic Committee for administering international competition in the aquatic sports FINA oversees competition in five aquatic sports: swimming, diving, synchronized swimming, water polo and open water swimming.

Swimming and Disabilities

Since the first Paralympic Games in Rome in 1960, swimming has been one of the main sports at the Paralympics. As in the Olympic Games, competitors measure their skills in freestyle, backstroke, butterfly, breaststroke and medley events. Athletes are classified based on their functional ability to perform each stroke.

Paralympic swimming is governed by the International Paralympic Committee (IPC) and co-ordinated by the IPC Swimming Technical Committee, which incorporates the rules of the International Swimming Federation (FINA). The FINA rules are followed with a few modifications, such as optional platform or in-water starts for some races and the use of signals or ‘tappers’ for swimmers with blindness/visual impairment. However, no prostheses or assistive devices are permitted.

Find out more about swimming with BBC sport and Wikipedia.

Paralympics women's 100m Butterfly at Beijing Paralympic Games

Paralympic swimming classifications