The Women's 400m Freestyle on Saturday sets up as the Race of the Century.
Katie Ledecky is pursuing her eighth gold medal and if she wins three medals, her total of 13 will be the most for any female swimmer. Ledecky will match up against her main rival, Australia's Ariarne Titmus, with Canada's Summer McIntosh in position to win gold if either of the previous two Olympic gold medalists falters.