Croatia competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's eighth consecutive appearance at the Summer Olympics.
Japan competed as the host nation of the 2020 Summer Paralympics in their capital Tokyo from 24 August to 5 September 2021.
The men's tournament of water polo at the 2020 Summer Olympics at Tokyo, Japan began on 25 July and ended on 8 August 2021. It was held at the Tokyo Tatsumi International Swimming Center. It was the 27th official appearance of the tournament, which was not held in 1896 and was a demonstration sport in 1904 but otherwise had been held at every Olympics.
Turkey competed at the 2020 Summer Paralympics in Tokyo, Japan from 24 August to 5 September 2021. This was the country's seventh appearance in the past eight Games despite their absence in the 1996 Summer Paralympics.
Montenegro competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's fourth consecutive appearance at the Summer Olympics since gaining independence in 2006.
These are the rosters of all participating teams at the men's water polo tournament at the 2020 Summer Olympics in Tokyo. The twelve national teams were required to submit squads of 12 players. Additionally, teams could name one alternate player. In the event that a player on the submitted squad list suffered an injury or illness, that player would be able to be replaced by the player in the alternate list. On 3 July 2021, the International Olympic Committee (IOC) confirmed that there was a change for the 2020 Summer Olympics, allowing all 13 water polo players named to be available on the roster, with 12 being named for each match. This change was implemented due to the challenges of the COVID-19 pandemic. As of 2 August 2021, all players competed in the men's tournament.
The men's single sculls competition at the 2020 Summer Paralympics in Tokyo took place at the Sea Forest Waterway.
The women's single sculls competition at the 2020 Summer Paralympics in Tokyo took place at the Sea Forest Waterway.
The Women's 100 metre freestyle S10 event at the 2020 Paralympic Games took place on 28 August 2021, at the Tokyo Aquatics Centre.
The Women's 200 metre freestyle S14 event at the 2020 Paralympic Games took place on 27 August 2021, at the Tokyo Aquatics Centre.
The Women's 400 metre freestyle S13 event at the 2020 Paralympic Games took place on 27 August 2021, at the Tokyo Aquatics Centre.
The men's 50 metre freestyle S11 event at the 2020 Paralympic Games took place on 27 August 2021, at the Tokyo Aquatics Centre.
The men's 200 metre freestyle S14 event at the 2020 Paralympic Games took place on 27 August 2021, at the Tokyo Aquatics Centre.
The men's 400 metre freestyle S13 event at the 2020 Paralympic Games took place on 27 August 2021, at the Tokyo Aquatics Centre.
The men's 100 metre breaststroke SB5 event at the 2020 Paralympic Games took place on 28 August 2021, at the Tokyo Aquatics Centre.
The men's 100 metre breaststroke SB6 event at the 2020 Paralympic Games took place on 28 August 2021, at the Tokyo Aquatics Centre.
The men's 50 metre butterfly S5 event at the 2020 Paralympic Games took place on 27 August 2021, at the Tokyo Aquatics Centre.
The men's 150 metre individual medley SM4 event at the 2020 Paralympic Games took place on 28 August 2021, at the Tokyo Aquatics Centre.
The men's 200 metre individual medley SM8 event at the 2020 Paralympic Games took place on 28 August 2021, at the Tokyo Aquatics Centre.
