Though paralyzed from the waist down, William Stock was a strong swimmer who could swim unaided the quarter-mile to Flat Island in Kailua Bay and used to swim at Kaiser's in big waves, his son Jacob said.

So Stock's death, after being found unconscious underwater near a drain in the Hilton Hawaiian Village lagoon, puzzles family and friends.

A man who helped rescue Stock says it appeared that Stock was held underwater after his leg was caught by the suction of the drain.

“;This needs to get looked into,”; said Jacob Stock, 21, one of his two sons. “;If it could happen to my dad, it could happen to anyone.”;

Dr. William Goodhue, the Honolulu Medical Examiner's first deputy who performed the autopsy on William Stock, and investigators visited the lagoon yesterday with a Hilton employee to inspect the scene of the accident.

Goodhue's final autopsy report will be ready in about 30 days, but he has ruled the cause of death as a “;near drowning.”;

Stock, 56, of Foster Village, was taken off life support last Friday when it was determined he was brain dead, said longtime friend Robert Peine.

Hilton Hawaii's area vice president and managing director, Jerry Gibson, issued a written statement: “;We are greatly saddened by this incident and wish to express our condolences to Mr. Stock's family. We are cooperating with local authorities to investigate the matter.”;

Hilton declined to answer Star-Bulletin questions yesterday about the July 30 accident.

On that day at about 11:30 a.m., Texas visitor Scott King was celebrating his birthday with his family at the busy lagoon when he heard a girl scream after spotting a man unconscious underwater near a buoy.

Another man was “;trying to hold his head out of the water and said he couldn't get him out because his leg got caught in the drain,”; King said.

It appeared suction from the drain was holding his leg, “;because there was nothing really pinning him,”; King said.

Finally, after much urging, a hotel surf instructor joined King and the other man and pulled Stock free, King said. There did not appear to be a lifeguard at the lagoon, he added.

King estimated Stock was underwater for 10 to 12 minutes; his face had changed color and his eyes were rolled back.

A bystander administered cardiopulmonary resuscitation, and a security guard arrived a few minutes later and continued CPR until paramedics took Stock to the hospital.

“;Once they took him, everything went on like nothing happened,”; King said. “;They didn't warn anybody, they didn't rope anything off, nothing.

“;They had kids within minutes playing on the same rock where this guy was stuck,”; he said.

The Hilton restored the 5-acre man-made Duke Paoa Kahanamoku Lagoon, built in the 1950s, in 2007.

The once-murky but now blue lagoon features a “;state-of-the-art water circulation system,”; the Hilton Web page says.