A 49-year-old swimmer who participated in the annual Waikiki Roughwater Swim died Monday after he ran into trouble halfway through the race — becoming the fourth person to die in ocean waters around Hawaii over the Labor Day weekend.

"It is very, very painful for everybody," said race director Kaia Hedlund.

At about 9:55 a.m., Hedlund said water safety personnel saw the swimmer in distress. Lifeguards brought the unresponsive swimmer to Kaimana Beach and administered CPR.

Paramedics transported the swimmer in critical condition to a hospital, where he died. The medical examiner’s office had not released the man’s identification Monday night. An autopsy will be held to determine the exact cause of death.

Hedlund said the death was the first for the annual Labor Day race.

Event media director Mike Lewis said the swimmer had registered just before the event.

"Without question, this is a tragedy that goes far beyond words," Lewis said.

"It pains us as an organization that this has happened," he added.

Organizers say safety at the event is paramount. Fifteen lifeguards and about 60 water safety volunteers are hired to closely monitor swimmers during the race.

In 2003, rescuers scrambled to pull more than 300 swimmers from treacherous waters when powerful currents hit during the race.

Nearly 1,000 swimmers participated in this year’s event. The 2.4-mile ocean swimming race starts at the New Otani Kaimana Beach Hotel and ends at the Hilton Hawaiian Village.

At about 11:05 a.m., a second swimmer who was not an event participant collapsed on the beach near the Hale Koa Hotel. Hedlund said water safety personnel with the event helped the swimmer.

Shayne Enright, spokeswoman for the Honolulu Emergency Services Department, said the swimmer in his 50s collapsed after he got out of the water. He was transported to an area hospital in critical condition.

Enright declined to comment specifically on the 49-year-old race swimmer’s death because event organizers hired their own lifeguards.

In addition to the Roughwater Swim participant, three other people died in ocean waters during the Labor Day weekend.

» At about noon off Kaanapali, Maui, on Saturday, Greg Ira Eveloff, 60, of Scottsdale, Ariz., was swimming with his family near the Sheraton Resort when he experienced difficulties. Fire rescue and paramedics responded. CPR was administered to no avail and Eveloff died at the scene.

» About two hours later in Laie on Oahu, Dante Biacan, 38, of Waipahu lost consciousness in the ocean. Paramedics picked up Biacan at Malaekahana State Recreation Area and transported him in extremely critical condition to a hospital, where he died.

» At about 12:35 p.m. Sunday, a 41-year-old man died after he was found unconscious in the ocean at Ko Olina. The medical examiner’s office identified him as Carl H. Wolfe of Kapolei. Police said Wolfe was snorkeling when he was found unconscious. He was transported in critical condition to an area hospital, where he later died.

Autopsies will be conducted on Wolfe, Biacan and Eveloff.

During a news briefing Monday at Ala Moana Beach Park’s Magic Island, Enright said, "Our condolences go out to all the family and friends who were impacted by these recent tragedies over the weekend."

Biacan and Wolfe were in waters where there are no lifeguards when they ran into trouble.

Enright said, "Such heartbreaking events, we must emphasize that people must swim where a lifeguard is watching."

"Our lifeguards are here because we know the ocean can be extremely dangerous," she added. She advised beachgoers to ask lifeguards questions on ocean safety, as well as locals who frequent the waters. "They’re the ones who know the currents, they know the surf breaks, they know the shore breaks. They’ll be able to tell you if this is a good area for you to go into or not."

She also recommended beachgoers carry a cellphone because minutes count when an emergency occurs.