Swimming has been another staple of the Modern Olympics, with Paris 1896 including a 100m freestyle for sailors.
Thirty-five events will make up the Tokyo programme, with men's 800m freestyle, women's 1500m freestyle and mixed 4x100m medley relay added for the first time.
World records have become commonplace in the pool, making this one of the most popular Olympic sports.
The United States have absolutely dominated swimming at the Games, winning 246 gold among their 553 medals. Australia comes next with 60 and 188 respectively.
That superiority was reflected at Rio 2016, where the Americans took out 16 events - Australia and Hungary were next with three each. Michael Phelps added to his illustrious career, with two individual golds and three more in relays, making 23 across four Olympics.
New Zealand has won six Olympic swimming medals, highlighted by Danyon Loader's freestyle double at Atlanta 1996.
Our medal hopes at Tokyo will rest with medley specialist Lewis Clareburt, who has won world championship and Commonwealth Games bronze over 400m.
Lewis Clareburt - men's 200m & 400m individual medley
Erica Fairweather - women's 200m & 400m freestyle
Ali Galyer - women's 100m & 200m backstroke
Hayley McIntosh - women's 1500m freetyle
Zac Reid - men's 400m & 800m freestyle
Eve Thomas - women's 800m & 1500m freestyle
Carina Doyle, Fairweather, Galyer & Thomas - women's 4x200m freestyle relay
Five to Watch
Katie Ledecky (United States)
Ledecky has five golds from the past two Games and needs three more to equal retired compatriot Jenny Thompson's record eight for a female swimmer (1992-2000).
At Rio 2016 she won four golds and a silver and was the most decorated female athlete along with U.S. gymnast Simone Biles. In Tokyo she can win the 800m free for the third Games in a row, having first won it in London as a 15-year-old.
Ledecky, 24, also has 15 world championship golds and holds the world records for 400, 800 and 1,500m freestyle.
Caeleb Dressel (United States)
A double Olympic relay gold medallist in 2016 and winner of 13 world championship golds, the 24-year-old sprint specialist is another U.S. medal machine.
In 2019 Dressel became the first swimmer to win eight medals at a single world championships and also took Olympic great Michael PhelpsΓÇÖs 10-year-old 100m butterfly world record for good measure.
He will be favourite in the 50 and 100m free and the 100m butterfly. Throw in the relays and he could be targeting seven golds.
Ariarne Titmus (Australia)
The 20-year-old Tasmanian will be making her Olympic debut with plenty of expectation after winning two golds at the 2019 world championships including beating an unwell Ledecky to the 400m freestyle title.
She came back from a three-month layoff with a left shoulder problem by taking the 200m freestyle title at Australia's national championships in April.
The showdown between her and Ledecky, the two fastest women in 400m history, promises to be a highlight.
Adam Peaty (Great Britain)
The breaststroke specialist, the reigning Olympic champion and world record holder at 100m, is as close as it gets to a nailed-on certainty in the pool.
The 26-year-old Briton is the only man to have swum the 100m in under 58 seconds and he now has the top 20 fastest times in history. During the COVID-19 lockdown he had a pool installed in his back garden.
"For me, as a personal journey, it's all about breaking world records and going faster," the eight times world champion said in March.
Kristof Milak (Hungary)
Olympic debutant Milak could be a threat to Dressel in the 100m butterfly and that duel will be eagerly awaited.
The 21-year-old is Hungary's rising star, taking some of the attention away from 'Iron Lady' compatriot Katinka Hosszu, after smashing Phelps's decade-old 200m butterfly world record at the 2019 worlds.
At the European championships in Budapest in May, he won the 200m fly by more than three seconds and posted the second fastest time ever in the distance.