(L-R) Tamsin Cook of Australia, Lauren Boyle of New Zealand, Boglarka Kapas of Hungary, Katie Ledecky of the United States and Sharon van Rouwendaal of the Netherlands compete in the Women's 400m Freestyle heat on Day 2 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 7, 2016 in Rio de Janeiro, Brazil.

Katie Ledecky of the United States competes in the Women's 400m Freestyle Final on Day 2 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 7, 2016 in Rio de Janeiro, Brazil.

Leah Smith of the United States competes in the Women's 400m Freestyle heat on Day 2 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 7, 2016 in Rio de Janeiro, Brazil.

General view of the Women's 400m Freestyle Final on Day 2 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 7, 2016 in Rio de Janeiro, Brazil.

Leah Smith of the United States of America competes in the Women's 400m Freestyle heat on Day 2 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 7, 2016 in Rio de Janeiro, Brazil.

Jazz Carlin of Great Britain competes in the in the Women's 400m Freestyle heat on Day 2 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 7, 2016 in Rio de Janeiro, Brazil.

Katie Ledecky of the United States of America competes in the Women's 400m Freestyle Final on Day 2 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 7, 2016 in Rio de Janeiro, Brazil.

Yang Sun of People's Republic of China competes in heat six of the Men's 400m Freestyle on Day 1 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on August 6, 2016 in Rio de Janeiro, Brazil.

Connor Jaeger of the United States, Yang Sun of People's Republic of China and Park Tae-hwan of Republic of Korea compete in heat six of the Men's 400m Freestyle on Day 1 of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on on August 6, 2016 in Rio de Janeiro, Brazil.

Nanjing 2014 - Gold medalist Mykhailo Romanchuk of Ukraine(C), silver medalist Maecelo Alberto Acosta of El Salvador(L) and bronze medalist Henrik Christiansen of Norway pose on the podium during the awarding ceremony of Men's 400m Freestyle of Nanjing 2014 Youth Olympic Games in Nanjing, capital of Jiangsu Province, on Aug. 17, 2014.