Indianapolis, Indiana - Simone Manuel will go for gold in the 50m freestyle at a third straight Olympics in Paris after snatching victory at the US swimming trials on Sunday by two-hundredths of a second.

Manuel, who won 100m freestyle gold and 50m free silver at the Rio Olympics but struggled through a disappointing Tokyo campaign as she battled the effects of over-training syndrome, clocked 24.13sec to edge Gretchen Walsh, the top seed going into the final who had opened her trials with a world record in the 100m butterfly.

As she checked the scoreboard, Manuel shook her head and smiled, the crowd at Lucas Oil Stadium – home of the NFL's Indianapolis Colts – erupting in cheers.

"Yes and no," she said when asked if she surprised herself. "I put in a lot of work to get to this point.

"I wasn't feeling too confident after last night," added the 27-year-old, who posted just the fourth-fastest time in Saturday's semi-finals.

"I spent a lot of time watching races where I won. I really wanted to channel that Simone, because I know I'm a winner and that's what I did tonight."

Manuel's 100m free victory in Rio made her the first African-American woman to win an individual Olympic swimming medal. But she struggled through the trials for the pandemic-delayed Tokyo Games, where she finished out of the medals in the 50m free.

Now, she said, she's focused on getting faster, and having some fun with her teammates.

"The last experience was tough for me, but I still had amazing teammates that got me through it and so I'm just looking for a really fun experience with Team USA this summer," she said.

In the final event of the nine-day trials, Bobby Finke lined up a second gold medal defense with a victory in the 1500m freestyle in 14:40.28sec – second-fastest in the world this year.

Behind him, David Johnston held off hard-charging Luke Whitlock to book his first trip to the Olympics, finishing second in 14:52.74.

Johnston erased the disappointment of third- and fourth-place finishes earlier in the meet, clocking a personal best that met the Olympic qualifying standard to ensure he is, indeed, on his way to Paris.

"It took everything I had to get to that wall," Johnston said. "I mean, my legs at the 300 meter (mark) were completely gone, and I just had to fight with everything I had to get there."

"I'm just glad I kind of saved my meet," added Johnston, who called coming up empty in the 400m and 800m freestyle "devastating."

"I feel like I've learned a lot this week that I'm going to be able to take forward into the future," he said.

Finke, who exploded on the international scene with surprise wins in the 800m and 1500m free in Tokyo, will defend both titles in Paris and said he was looking forward to getting back to the sport's biggest stage.

And even though his status as defending champion in the 800m and 1500m free ramps up the pressure it won't change his mindset.

"I'm always going in just trying to race it and do my best," he said.