It is difficult to find an Olympic sport that has undergone such a dramatic change as swimming.
What is now one of the glamour events of the Games takes place in 50-metre, temperature-controlled pools with lane makers designed to reduce turbulence and wave-killing gutters.
But conditions at early Olympiads were as a conducive to setting fast times.
Venues included the Bay of Zea at Athens in 1896, the River Seine at Paris 1900 and a 100m pool constructed inside the athletics track at White City when London staged the Games in 1908.
Some of the events were even more bizarre - the 100m race for Greek sailors in 1896, underwater and obstacle races in Paris and plunge for distance in 1908.
In 1908, the Fédération Internationale de Natation (FINA) was founded to unify the rules and women's events were introduced at Stockholm in 1912.
In the Games swimming now consist of 34 races.
A maximum of eight swimmers contest each race and preliminary heats in the 50m, 100m and 200m races lead to semi-finals and finals based on the fastest times.
In events covering 400m or more and relays, the eight fastest finishers in the heats go straight to the finals
Diving is one of the most exhilarating sports at the Games, with platform divers hitting the water at about 55 kilometres an hour. It was introduced to the Olympics in 1904 and the programme did not change between 1924 and 1996.
Synchronised diving for pairs was introduced at Sydney in 2000 and there are now eight events, with the traditional 10m platform and 3m springboard diving for men and women repeated in synchronised diving.
Competitors make a series of dives combining somersaults, pikes, tucks and twists and judges mark out of 10, taking approach, take-off, execution and entry into the water into consideration.
Points are adjusted depending on the degree of difficulty, based on the type and number of manoeuvres attempted.
Synchronised diving is also judged on how the pairs mirror height, distance from the springboard or platform, speed of rotation and entry into the water.
Water polo is one of the most physically demanding sports in the Olympics.
The players need the endurance to get through four seven-minute quarters of a match without touching the bottom or side of the pool, and can swim up to five kilometres during a game.
Passing, dribbling and shooting technique is just as crucial, as is the strength to battle for the ball, with grabbing, holding and kicking not uncommon in a sport where 85 per cent of the body is submerged.
The sport was included in the 1900 Games, with women's waterpolo introduced in 2000.
There are 12 teams in the men's competition and eight in the women's.
Synchronised swimming, an exhibition sport from 1948 to 1968, made its full debut at Los Angeles in 1984.
It is open only to women, who perform technical and free routines to music in duet and team events.
Breath control is key as strenuous manoeuvres are performed underwater and upside down.
Underwater speakers let the swimmers hear the music and achieve the split-second timing critical to the event.
Swimming has produced the two biggest mutliple winners in Olympic history. First, Mark Spitz won seven gold medals at the 1972 Games in Munich, a record many said would never be broken, only for fellow American Michael Phelps to come along and win eight titles at Beijing in 2008.
The sport has always produced some of the Olympics' most charsamatic figures, including the Australian Dawn Fraser, who won the 100 metres freestyle for three consecutive Games between 1956 and 1964 only to be banned for 10 years after Tokyo for climbing a flagpole at Emperor Hirohito's Palace to steal the Olympic flag for a souvenir.
Arguably the most famous diver in Olympic history is Greg Louganis, who at Seoul in 1988 cracked his head on the springboard while attempting a reverse 2.5 spike. After receiving stitches, Louganis won gold in both men's events.
Britain dominated the early water polo tournaments, winning the gold medal in three of the four first Olympics it was staged. But the sport is no longer widely popular in Britain, unlike in Hungary, who have established themselves as the true Olympic masters, claiming the title on a record nine occasions, including the three last Games.
The United States, Canada and Japan have traditionally been the strongest nations in synchronised swimming, winning every Olympic medal from 1984 through to 1966, but Russia has recently become the dominant nation, claiming every every in 2000, 2004 and 2008.
Swimmers have broken 62 records since the launch of Speedo's LZR Racer in February 2008, including Michael Phelps and Britain's Rebecca Adlington, and 94 per cent of the gold medallists in Beijing in 2008 wore the controversial suit.
Johnny Weissmuller, the 1924 and 1928 100 metres freestyle champion, was the first of four Olympic medallists to play the part of Tarzan. He made his debut in 1932 in Tarzan, the Ape Man after being spotted swimming on Sunset Boulevard.