Swimming at the Rio Olympics

Nathan Adrian (USA) dives in for the final length during the men's 4x100 medley relay final.

Michael Phelps (USA) swims during the men's 4x100-meter medley relay.

Ryan Murphy (USA) starts the men's 4x100 medley relay final.

Kathleen Baker , Lilly King, Dana Vollmer and Simone Manuel celebrate after winning the women's 4x100-meter medley relay.

Lilly King (USA) swims during the women's 4x100-meter medley relay.

Dana Vollmer (USA) swims during the women's 4x100-meter medley relay.

Simone Manuel (USA) swims during the women's 4x100-meter medley relay.

Connor Jaeger (USA) after taking second in the men's 1,500-meter freestyle final.

Gregorio Paltrinieri (ITA) celebrates with Gabriele Detti (ITA) after the men's 1,500-meter freestyle final.

Pernille Blume (DEN) reacts after winning the women's 50-meter freestyle.

Connor Jaeger (USA) swims during the men's 1,500-meter freestyle final.

Gregorio Paltrinieri (ITA) swims during the men's 1,500-meter freestyle final.

Anthony Ervin celebrates with his gold medal in the men's 50-meter freestyle.

Anthony Ervin celebrates after winning the men's 50-meter freestyle final.

Katie Ledecky celebrates after winning the women's 800-meter freestyle.

Katie Ledecky takes a big lead in the women's 800-meter freestyle final.

Joseph Schooling of Singapore celebrates after winning the men's 100-meter butterfly final.

Michael Phelps reacts with Laszlo Cseh of Hungary after they both finished as part of a three-way tie for silver in the men's 100-meter butterfly.

Michael Phelps during the men's 100-meter butterfly final.

Maya Dirado reacts after winning the women's 200-meter backstroke.

Maya Dirado swims during the women's 200-meter backstroke final.

Simone Manuel (USA) reacts after getting gold in the women's 100-meter freestyle final.

Simone Manuel (USA) hugs Penny Oleksiak (CAN) after they tied for gold in the women's 100-meter freestyle.

Simone Manuel (USA) celebrates after getting a tie for gold in the women's 100-meter freestyle final.

Simone Manuel (USA) during the women's 100-meter freestyle.

Michael Phelps and Ryan Lochte react after the men's 200-meter individual medley.

Michael Phelps (USA) holds up four fingers, for his fourth gold of the Rio Games, after winning the men's 200-meter individual medley.

Michael Phelps (USA) races Ryan Lochte (USA) during the men's 200-meter individual medley.

Michael Phelps (USA) races Ryan Lochte (USA) during the men's 200-meter individual medley.

Michael Phelps (USA) swims in the men's 200-meter individual medley.

Ryan Murphy (USA) celebrates after winning the men's 200-meter backstroke final.

Ryan Murphy celebrates after winning the men's 200-meter backstroke final.

Ryan Murphy (USA) swims during the men's 200-meter backstroke final.

Maya Dirado (USA) swims during the women's 200-meter backstroke semifinal.

Missy Franklin (USA) and Maya Dirado (USA) react after the women's 200-meter backstroke semifinal.

Long Gutierrez Feng (MEX) during the men's 100m butterfly heats.

Swimmers in the start blocks during the men's 50m freestyle heats.

Michael Phelps (USA) during the men's 100m butterfly heats.

Yaxin Liu (CHN) during the women's 200m backstroke heats.

The U.S. team of Maya Dirado, Allison Schmitt, Leah Smith and Katie Ledecky celebrate after winning the women's 4x200-meter freestyle relay.

Team USA celebrates after winning the women's 4x200-meter freestyle relay.

Allison Schmitt started off the women's 4x200-meter freestyle relay for the United States.

Michael Phelps (USA) and Ryan Lochte (USA) swim during the men's 200-meter individual medley semifinals.

Michael Phelps (USA) and Ryan Lochte (USA) react after the men's 200-meter individual medley semifinals.

Lilly King (USA) swims during the women's 200-meter breaststroke semifinals.

Mirela Belmonte Garcia (ESP) celebrates after winning the women's 200-meter butterfly.

Mireia Belmonte Garcia (ESP) swims during the women's 200-meter butterfly.

Kyle Chalmers (AUS) celebrates after winning the men's 100-meter freestyle.

Nathan Adrian (USA) greets Kyle Chalmers (AUS) after the men's 100-meter freestyle final. Adrian took third.

Nathan Adrian (USA) swims during the men's 100-meter freestyle final.

Hali Flickinger (USA) greets Cammille Adams (USA) after the women's 200-meter butterfly final.

Simone Manuel (USA) swims during the women's 100-meter freestyle semifinals.

Ryan Murphy (USA) swims during the men's 200-meter backstroke semifinals.

Jacob Pebley (USA) swims during the men's 200-meter backstroke semifinals.

Guangyuan Li (CHN) reacts after the men's 200-meter backstroke semifinals.

Dmitriy Balandin (KAZ) celebrates after winning the men's 200-meter breaststroke final.

Josh Prenot swam to a second-place finish in the men's 200-meter breaststroke final.

Michael Phelps (USA) during the men's 200m individual medley heats in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Michael Phelps (USA) during the men's 200m individual medley heats in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Rexford Tullius (ISV) during the men's 200m backstroke heats.

Abbey Weitzeil (USA) during the women's 100m freestyle heats.

Simone Manuel (USA) during the women's 100m freestyle heats.

Michael Phelps (USA) , Masato Sakai (JPN) and Tamas Kenderesi (HUN) with their medals after the men's 200m butterfly final in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Sarah Sjostrom (SWE) , Katie Ledecky (USA) and Emma Mckeon (AUS) with their medals after the women's 200m freestyle final in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Katinka Hosszu (HUN) reacts after winning the women's 200m individual medley final in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Michael Phelps during the 200-meter butterfly final. He won the race for his 20th career gold medal.

Katie Ledecky celebrates after winning the women's 200-meter freestyle final.

Duo Shen of China during the women's 200-meter freestyle final.

Caeleb Dressel of the U.S. competes in the men's 100-meter freestyle semifinal.

Caeleb Dressel (USA) and Nathan Adrian (USA) after the men's 100m freestyle heats in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Natalie Adams (USA) during the women's 200m butterfly heats in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Natalie Adams (USA) blows a kiss after the women's 200m butterfly heats in the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Lilly King (USA) celebrates winning during the women's 100m breaststroke final.

Lilly King (USA) celebrates winning the women's 100m breaststroke final.

Lilly King (USA) and Katie Meili (USA) celebrate after the women's 100m breaststroke final.

Lilly King (USA) swims in the women's 100m breaststroke final.

Lilly King (USA) races during the women's 100m breaststroke final.

Ryan Murphy (USA) and David Plummer (USA) pose with their medals after the men's 100m backstroke final.

Ryan Murphy (USA) celebrates with David Plummer (USA) after the men's 100m backstroke final. Murphy won, and Plummer placed second.

David Plummer (USA) and Ryan Murphy (USA) react after the men's 200m freestyle final.

Ryan Murphy (USA) swims in the men's 100m backstroke final.

Katinka Hosszu (HUN) celebrates after winning the women's 100m backstroke final.

Kathleen Baker (USA) celebrates on the podium after the women's 100m backstroke final.

Conor Dwyer (USA) with his bronze medal after the men's 200m freestyle final.

Yang Sun (CHN) celebrates after winning the men's 200m freestyle final.

Yang Sun (CHN) celebrates on the podium after winning the men's 200m freestyle final.

Michael Phelps (USA) competes during the men's 200m butterfly semifinals.

Katie Ledecky (USA) swims during the women's 200m freestyle semifinals on Monday.

Michael Phelps (USA) in the men's 200m butterfly heats.

Missy Franklin (USA) in the women's 200m freestyle preliminary heats.

Maya Dirado (USA) in the women's 200m individual medley heats.

Duo Shen (CHN) in the women's 200m freestyle preliminary heats.

Melania Costa Schmid (ESP) in the women's 200m freestyle preliminary heats.

Tamas Kenderesi (HUN) in the men's 200m butterfly heats.

Sarah Sjostrom (SWE) in the women's 200m freestyle preliminary heats.

Camille Cheng (HKG) in the women's 200m freestyle preliminary heats.

Melania Costa Schmid (ESP) in the women's 200m freestyle preliminary heats.

USA's Katie Ledecky and Leah Smith celebrate with their medals after the women's 400m freestyle final.

USA's Nathan Adrian , Ryan Held , Michael Phelps and Caeleb Dressel celebrate with their gold medals after the men's 4x100m freestyle relay final.

Michael Phelps (USA) and Caeleb Dressel (USA) celebrate after winning the men's 4x100m freestyle relay.

Nathan Adrian celebrates after anchoring the USA to victory during the men's 4x100m freestyle relay final.

Michael Phelps helped the U.S. men's 4x100m freestyle relay team take gold.

Michael Phelps swam the second leg for the U.S. men's 4x100m freestyle relay team.

Michael Phelps preps for the men's 4x100m freestyle relay final.

Michael Phelps (USA) leads his relay teammates to the pool before the men's 4x100m freestyle relay final.

Leah Smith (USA) and Katie Ledecky (USA) celebrate after the women's 400m freestyle final. Ledecky won, and Smith placed third.

Katie Ledecky (USA) celebrates with Leah Smith (USA) after winning the women's 400m freestyle final.

Katie Ledecky (USA) celebrates after winning the women's 400m freestyle final, breaking her own world record in the process.

Katie Ledecky (USA) preps for the women's 400m freestyle final.

Cody Miller (USA) celebrates on the podium after placing third in the men's 100m breaststroke final.

Adam Peaty (GBR) celebrates after winning the men's 100m breaststroke final.

Adam Peaty (GBR) and Cody Miller (USA) celebrate after the men's 100m breaststroke final. Miller came in third.

Dana Vollmer (USA) receives her bronze medal on the podium after the women's 100m butterfly final.

Sarah Sjostrom (SWE) reacts after setting a world record during the women's 100m butterfly final.

Dana Vollmer (USA) reacts after placing third in the women's 100m butterfly final.

Sarah Sjostrom (SWE) swims during the women's 100m butterfly final.

Lilly King (USA) swims during the women's 100m breaststroke heats.

David Plummer (USA) swims during the men's 100m backstroke heats.

Mitchell Larkin (AUS) during the men's 100m backstroke heats.

Jimmy Feigen (USA) greets Anthony Ervin (USA) after the men's 4x100m freestyle relay heats.

Corey Main (NZL) during the men's 100m backstroke heats.

Katinka Hosszu (HUN) during the women's 100m backstroke heats.

USA team members Simone Manuel , Abbey Weitzeil , Dana Vollmer and Katie Ledecky on the podium with their medals after the women's 4x100m freestyle relay finals during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Australia team members celebrate after winning the women's 4x100m freestyle relay finals during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Maya Dirado (USA) celebrates after the women's 400m individual medley final during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Katinka Hosszu (HUN) in the women's 400m individual medley final during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Kosuke Hagino (JPN) celebrates after winning the men's 400m individual medley final during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Dana Vollmer (USA) in the women's 100m butterfly semifinals during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Chase Kalisz (USA) in the men's 400m individual medley final during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Chase Kalisz (USA) stretches before the men's 400m individual medley final during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Connor Jaeger (USA) and Yang Sun (CHN) after the men's 400m freestyle heats during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Conor Dwyer (USA) in the men's 400m freestyle heats during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Maya Dirado (USA) in the women's 400m individual medley heats during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Ross Murdoch (GBR) in the men's 100m breaststroke heats during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium.

Katie Ledecky (USA) swims in the women's 4x100m freestyle relay heats during the Rio 2016 Summer Olympic Games at Olympic Aquatics Stadium. Mandatory

Katinka Hosszu (Hungary) in the women's 400m individual medley.

Conor Dwyer (USA) reacts after the men's 400m freestyle heats.

Ziao Qiu (CHN) in the men's 400m freestyle heats.

Daynara de Paula (BRA) reacts after winning a women's 100m butterfly heat.

Chase Kalisz (USA) dives in at the start of the men's 400m individual medley heat.