The location for open-water events was a source of concern for athletes since scientists have found microbes in the waters off of Fort Copacabana and drug-resistant super bacteria off the beaches of Rio de Janeiro in 2014 and 2016 studies due to the daily dumping of hospital waste and household raw sewage into the rivers and ocean. Ten percent of the Copacabana water test samples contained drug-resistant super bacteria. However, during the races the water quality was good.
Events
Similar to the program's format in 2012, swimming features a total of 34 events, including two 10 kmopen-water marathons. The following events will be contested :
Similar to previous Olympics since 2000, with the exception of 2008, the swimming program schedule will occur in two segments. For the pool events, prelims are held in the afternoon, followed by the semifinals and final in the evening and night session. The dates in the table are for August.
FINA By-Law BL 9.3.6.4 and BL 9.3.7.5.3 laid out the qualification procedures for the "Swimming" competition at the Olympics. Each country is allowed to enter up to two swimmers per individual event, and one entry per relay; and a country may not have more than 26 males and 26 females on its team.
On January 15, 2015, FINA posted the qualifying times for individual events for the 2016 Summer Olympics. The time standards consisted of two types: an "Olympic Qualifying Time" and an "Olympic Selection time". Each country was able to enter up to two swimmers per event, provided both swimmers met the qualifying time. A country was able to enter one swimmer per event that met the invitation standard. Any swimmer who met the "qualifying" time was entered in the event for the Games; a swimmer meeting the "invitation" standard was eligible for entry, and their entry was allotted/filled in by ranking. If a country had had no swimmers who meet either qualifying standard, it may have entered one male and one female. A country that did not receive an allocation spot but had at least one swimmer who met a qualifying standard might have enter the swimmer with the highest ranking.
9: the top-9 finishers at the 2016 Olympic Marathon Swim Qualifier
5: one representative from each FINA continent.
1: from the hostnation if not qualified by other means. If Brazil already contained a qualifier in the race, this spot had been allocated back into the general pool from the 2016 Olympic qualifier race.
Participation
Participating nations
Brazil, as the host country, receives guaranteed quota place in case it would not qualify any qualification places.
Medal summary
Medal table
;Key Host nation
Men's events
Swimmers who participated in the heats only and received medals.
Women's events
Swimmers who participated in the heats only and received medals.
