US Olympian and two-time All-American swimmer Richard Thornton collapsed and died on a California beach Thursday, according to his family.

He was 65.

The avid surfer was meeting with a friend at The Hook, a popular spot to catch waves in Santa Cruz, his brother, Marc Thornton, told ABC 7.

“He was following his buddy down the steps,” Marc Thornton added.

“His buddy jumped in the water, looked up for Richard, and Richard was just standing there at peace, not clutching his heart or anything, and he just kind of collapsed into the water.”

Thornton’s daughter, Kirra, blasted reports that the swimmer died in a surfing accident and said the cause of death was unknown.

Thornton had been battling Multiple Myeloma, his family told the outlet.

Marc Thornton shared that his brother died “doing what he loved” in a Facebook post.

“He could be in a hospital for six months with an oxygen tube, losing weight and all that,” Marc told the outlet. “What a way to go for someone who loved the beach and being in the water.”

Thornton, then 21, qualified and was selected as a member of the US men’s Olympic swimming team in 1980.

Thornton, however, opted not to participate and boycotted the Summer Olympic Games in Moscow in protest of the Soviet Union’s 1979 invasion of Afghanistan.

He later graduated with his bachelor’s degree in physical education from the University of Cal Berkeley in 1980.

Thornton specialized in the 100 and 200 butterfly and the 200 freestyle, according to his former alma mater.

“We are heartbroken to learn of the passing of Cal Swimming great Richard Thornton,” UC Berkeley’s Athletics department posted on X. “Our thoughts are with Richard’s family, friends, and all of those he impacted in the Cal community.”

Thornton had been the head coach of San Ramon Valley Aquatics since 1984.

Thornton had also coached the US national and junior national teams in Paris, Japan, and Brazil.

He was named Pacific Swimming Coach of the Year once after being nominated for six consecutive years between 1994 and 2000.

During his coaching career, Thornton coached several future Olympians, including Matt Biondi, who won eight gold medals in the 1984, ’88, and ’92 Olympic Games, according to Cal.

Thornton’s childhood friend Rob Werner said he could always be found in the water when he wasn’t training.

“I remember him telling me, in between meets or after meets or after the season, we were like let’s go surfing,” Rob Werner told ABC 7.

“I yelled from the stands after he won, ‘Richard, what are you going to do now?’ And he kind of goes like this in a surfing stance. He wanted to go surfing. That was his thing, man.”