An intrepid triathlete who served as an inspiration to her thousands of dedicated followers tragically drowned during the swimming endurance portion of the famed Ironman competition in Texas on Saturday.

Mara Flávia, a 38-year-old Brazilian influencer with more than 60,000 followers on Instagram, vanished during an open-water swim in Lake Woodlands, the first of three grueling trials competitors face during the 140-mile race.

Frantic calls started pouring in to the Montgomery County Sheriff’s Office and the Woodlands Township Fire Department as early as 6 a.m., Fox 26 reported. Woodlands Fire Chief Palmer Buck told Click2Houston that crews were first notified about the “lost swimmer” around 7:30 a.m.

The pro female swim started at 6:31 a.m., according to the Texas Ironman schedule.

Rescuers sifted through the lake while the triathlon was still ongoing, which Buck said contributed to the challenging conditions and worsened the dive team’s “zero” visibility.

Flávia was eventually pulled out of the water just after 9:30 a.m., roughly three hours after she disappeared. By then, her body had sunk down 10 feet to the bottom of the lake, Buck said.

She was pronounced dead on the shore.

The sheriff’s office confirmed that the victim “drowned while participating in the swim portion of the event,” according to a statement. The office said its Major Crimes unit will continue the investigation “per normal protocols.”

An Ironman volunteer heartbreakingly detailed the “panic and fear” he and other witnesses experienced when Flávia, whom none of them knew personally, vanished underneath the water.

“They all said the same thing: She went under. Right here. Right below us,” he recounted.

He said that one veteran racer clung to the side of a kayak with “a thousand-yard stare” because “he had just watched someone disappear beneath him.”

The selfless volunteer, who originally came out to help his young daughter “experience this incredible event from a completely different perspective,” dove under enough times that he “lost count” while trying to retrieve Flávia.

During his first attempt, he “felt her body” with one foot.

“She was gone. I don’t know how to describe what that felt like. I tried again. And again. And again. I just knew I would feel her again and could grab her and pull her up,” he wrote.

He admitted that he didn’t rationalize the risks he was taking until long after Flávia’s body was recovered.

“It never entered my mind that she had already passed long ago. I just kept searching like I was going to pull her up alive,” he wrote.

The volunteer hailed Flávia for “chasing something most people only dream of finishing.”

“She showed up for it. She deserved to come out of it,” he wrote.

“To her family: we did everything we could. I am so deeply, genuinely sorry that it wasn’t enough. She will stay with me,” he added.