TOKYO — Regan Smith was OK with seeing her world record broken. In fact, the Lakeville swimmer sent a congratulatory text to Australia's Kaylee McKeown, who took down Smith's two-year-old world mark in the women's 100-meter backstroke last month.

Being the pursuer rather than the pursuee just got Smith more excited for the Olympics, and an expected showdown with McKeown in the 100 back. Tuesday, McKeown kept the record and added an Olympic gold medal, becoming the first Australian woman to win the 100 back at the Summer Games. Canada's Kylie Masse took silver, and Smith earned the bronze medal in her first Olympic final.

Smith was never able to get to the lead. She was fourth at the halfway point, and she had too much distance to make up.

McKeown blazed through the final 50 meters in 29.27 seconds, passing Masse and Rhyan White of the U.S. Her winning time of 57.47 broke another of Smith's records, the Olympic mark she set in the semifinals. That was the fifth time the Olympic record was broken this week at Tokyo Aquatics Centre.

Smith finished in 58.05, .33 behind Masse. She said she was happy with her race and with the color of her medal.

"That's one of my best times ever,'' Smith said. "I really went out there and gave it my all. It was a super-stacked heat, so the fact that I came away with a medal, I really can't ask for much more.''

The U.S. ended the third day of swim finals with one gold medal and three bronze. The gold came in an event the Americans expected to win, but the victor came as a surprise.

In the women's 100 breaststroke, Lydia Jacoby, 17, defeated U.S. teammate Lilly King — the defending Olympic champ — and South Africa's Tatjana Schoenmaker. Schoenmaker was second and King third. Ryan Murphy gave the Americans a second bronze medal in the 100 back, finishing third in the men's event. Murphy also was the reigning Olympic gold medalist.

Smith was set to jump right back into the pool 8 ½ hours after the 100 back to begin her other individual event, the 200 butterfly. The heats are Tuesday evening Japan time (5:26 a.m. Central) and the semifinals are Wednesday morning (8:57 p.m. Central, Tuesday evening). She also is a candidate to swim in the women's 4x100 medley relay and the mixed medley relay.

Smith's coach, Mike Parratto, watched the race from his living room in Apple Valley. He said it looked like Smith did not have as sharp a start as she did in the semifinals, when her technique was outstanding on the start and the turn.

Still, Parratto thought Smith swam well in a race loaded with speed.

"I'm very proud of Regan,'' Parratto said. "An Olympic medal is an amazing achievement. Regan had a solid race, a great swim in a tough Olympic final.''

In mid-June, McKeown broke Smith's world record of 57.57, peeling .12 off Smith's time. Smith said she was "genuinely excited'' for McKeown, and she was motivated by the prospect of chasing the record again.

Smith said she was well prepared for the race, and even had been sleeping very well on the cardboard beds in the Olympic Village dorm rooms. But McKeown has been swimming fast all year, and she kept it up in a race that played out Monday evening in Tokyo.

McKeown touched the wall third in 28.20 at the 50-meter mark, with Masse first and White second. Her superior speed in the final 50 made her the youngest swimmer from her country to win an individual women's race at the Olympics in 41 years.

An exuberant McKeown was so overwhelmed by her victory that she cursed in a live poolside interview with Australian TV. She immediately put her hand to her mouth, realizing her faux pas.

"My legs were definitely hurting in the last 20 meters,'' McKeown said. "But I've trained for that. I knew I had a really good chance to be on the podium. I'm just thankful I've come away with the position that I have.''

In the 100 back heats and semifinals, the Olympic record changed hands four times. Masse, then Smith, then McKeown lowered the mark in three consecutive heats. Smith dropped it another notch in the semifinals, clocking a time of 57.86 before McKeown broke it again in the final.

That generated even more anticipation for a race that already was one of the most anticipated at the Olympic swimming venue. Though no fans are allowed, other swimmers and members of national delegations were permitted to attend, and Smith had a robust cheering section of Americans.

"Kaylee's been on fire this entire year,'' Smith said. "I knew she would have an amazing performance at these Games.

"This has just been so much fun. I've been loving village life, and competing has been a dream. I've just been trying to soak up every minute.''