Katie Ledecky has started the United States’ medal collection at the world swimming championships with a gold by reclaiming her title in the women’s 400 meters.

Adam Peaty of Great Britain celebrates after breaking a World Record 56.88 in the Men's 100m Breaststroke Semifinal on day one of the Gwangju 2019 FINA World Championships at Nambu International Aquatics Centre on July 21, 2019 in Gwangju,A couple of milliseconds make a world record of a difference. Swimming phenom Adam Peaty beat his own record time for the men's 100-meter breaststroke early Sunday, becoming the first man to finish the race in under 57 seconds. The 24-year-old Brit clocked in at 56.88, nearly two seconds ahead of his opponents, in the event's semifinals at the 2019 World Aquatic Championships in Gwangju, South Korea. He is scheduled to compete in the final round of the men's 100-meter breaststroke Monday. "I've come here to win a world title, and that's tomorrow, and that's still my main focus," he said.