A 54-year-old avid swimmer from California who participated in Monday’s Waikiki Roughwater Swim has died after he got into trouble during the race.

It was the first time Gustavo R. Penilla of Long Beach swam in the race, an event in which he looked forward to competing.

The annual Waikiki Roughwater Swim was held on Labor Day following a two-year hiatus due to the COVID-19 pandemic. More than 700 swimmers participated in the 2.4-mile race, which started at Sans Souci Beach and ended at Duke Kahanamoku Beach near the Hilton Hawaiian Village Resort.

About an hour after the race began, Ocean Safety, a private water safety company and a private canoe club responded to a swimmer in distress in waters off Waikiki.

Penilla was reportedly swimming when he stopped and rolled over. Other swimmers stopped and immediately alerted the safety crew.

Crews brought him to shore and administered cardiopulmonary resuscitation until Emergency Medical Services personnel arrived and took over with advanced life support.

Penilla was taken to The Queen’s Medical Center in critical condition, where he later died.

The Honolulu Medical Examiner’s Office determined the cause of death was drowning.

Close friend Kaia Hedlund of Long Beach, Calif., who has known Penilla for the past 15 years, said he was well-liked by many people. “This was a complete shock to everybody.”

Penilla grew up in Monterey Park, Calif. He graduated from the University of California-­Los Angeles and earned a master’s degree from California State University, Long Beach.

He had a great smile and was a spiritual person who always looked out for others, Hedlund said. “I can honestly say he’s probably the nicest, kindest person I know.”

When pools shut down after the COVID-19 pandemic began, Hedlund recalled how she and Penilla and other friends swam together in the ocean to stay active. “We would swim every day,” she said during a phone interview from California. “He was so fast. I couldn’t get anywhere near him.”

Penilla was an avid swimmer since childhood.

Hedlund said he always wanted to participate in the Waikiki Roughwater Swim and trained for months in the pool and ocean. He was very excited about it, she added.

Two weeks ago, Penilla participated in the 3-mile Naples Island Swim competition in California.

Sometime before the start of the Waikiki Roughwater Swim race Monday, he stood in front of the event banner to take photos with fellow swimmers from Long Beach who traveled to Hawaii to compete in the event.

Hedlund said Penilla will be best remembered for his kindness and warm smile.