2016 Rio Olympics - Swimming - Final - Men's 4 x 100m Freestyle Relay Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Michael Phelps (USA) of USA celebrates after they won. REUTERS/David Gray

2016 Rio Olympics - Swimming - Final - Men's 4 x 100m Freestyle Relay Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Michael Phelps (USA) of USA celebrates winning the gold medal. REUTERS/Dominic Ebenbichler

2016 Rio Olympics - Swimming - Final - Men's 4 x 100m Freestyle Relay Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. The USA team celebrates after winning. Picture rotated 180 degrees REUTERS/Athit Perawongmetha

2016 Rio Olympics - Swimming - Final - Men's 4 x 100m Freestyle Relay Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Michael Phelps (USA) of USA reacts after his team won the gold. REUTERS/Marcos Brindicci

2016 Rio Olympics - Swimming - Final - Men's 4 x 100m Freestyle Relay Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. The USA team celebrates after winning. REUTERS/David Gray

2016 Rio Olympics - Swimming - Victory Ceremony - Men's 4 x 100m Freestyle Relay Victory Ceremony - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Michael Phelps (USA), Ryan Held (USA), Caeleb Dressel (USA) and Nathan Adrian (USA) of USA pose with their medals. REUTERS/Stefan Wermuth

2016 Rio Olympics - Swimming - Victory Ceremony - Men's 4 x 100m Freestyle Relay Victory Ceremony - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Michael Phelps poses with his gold medal as he celebrates with his team. REUTERS/Marcos Brindicci

2016 Rio Olympics - Swimming - Victory Ceremony - Men's 4 x 100m Freestyle Relay Victory Ceremony - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Nathan Adrian (USA) of USA cries next to teammate Michael Phelps (USA) as they pose with their medals. REUTERS/Stefan Wermuth