Lazar Dukic, a 28-year-old Serbian athlete, was competing Thursday at Marine Creek Lake in Fort Worth, Texas, where the games were being held.

Dukic was approaching land and a finish line set up on the shore when he appeared to begin struggling.

"It was pretty devastating," visiting Canadian athlete Cole Learn told KXAS-TV.

"We were watching the athletes come in from their swim, and for some reason, I was watching Lazar. It looked like he was struggling a little bit."

The situation evolved "very, very quickly," Learn said, describing the swimmer's struggle to get air as he moved around in desperate circles.

Video from the incident shows the struggle just offshore, with officials intently watching the finish line, oblivious to what was happening a dozen yards away.

Lifeguards on paddleboards were reportedly similarly distracted by the finish line, totally missing Dukic's perilous situation.

"It happened so fast," Learn said. "There were 10 of us that saw it, we started screaming for the lifeguard. We were so far away, jumping in wouldn't have been an option."

Official event video, seen below, captured Dukic's peril.