Timothy Moy had arrived on O'ahu with his wife and son early for a conference and then planned to take a sabbatical from his teaching duties at the University of New Mexico.

Now, his drowning death while saving his 12-year-old son in Kailua Bay on Sunday has stunned his colleagues, said Patricia Risso, chairwoman of the university's history department.

"He's irreplaceable," Risso said. "He was brilliant. He knew his stuff very well and engaged the students. He was a fantastic lecturer."

Moy planned to take a break from teaching during a yearlong sabbatical, Risso said.

But first he was excited about attending an American Historical Association conference at the East-West Center — and excited about bringing his wife and only child to Hawai'i.

"It was going to be a special trip," Risso said.

Ocean safety officials said Moy's son got into trouble about 100 yards offshore around 2:30 p.m.

Moy went into the water to help his son, but ended up struggling himself, said Bryan Cheplic, spokesman for the city's emergency services department.

The 44-year-old was pulled ashore by a young man on a bodyboard.

"It was a little windy, maybe," Cheplic said. "But there was nothing out of the ordinary. The guy on the Boogie Board didn't seem to have any trouble bringing in the dad."

When paramedics arrived, both the son and father were on shore, and bystanders were administering cardiopulmonary resuscitation, he said.

"The boy seemed OK."

City lifeguards don't staff the beach near Wilikoki Place where the father and son fought the waves.

The son was taken to Castle Medical Center and was released Sunday night, said Jessica Lani Rich, president and executive director of the Visitor Aloha Society of Hawai'i. Rich said she had spoken to Moy's wife, Rebecca, yesterday.

"She's obviously very upset about what has happened to her husband so suddenly," Rich said. "They just want their privacy. Right now, her main concern is taking care of her son."

Moy's wife has friends on O'ahu who are helping her, Rich said, and the visitor's group also is assisting with funeral and travel arrangements.

The family is scheduled to return home to Albuquerque on Thursday, she said.

That's the same day that Moy, a popular associate professor who specialized in the history of science and technology, was scheduled to finish participating in the Pacific Coast Branch of the American Historical Association conference, which runs from today through Thursday.

Moy had an undergraduate degree from Harvard University and a Ph.D. from the University of California-Berkeley, and spent the past 14 years at the University of New Mexico.

He taught courses on the history of science in the western world, and science and technology in the United States. He also taught about science and technology for national security during the Cold War in a course called "Atomic America," Risso said.

This year, Moy was recognized as a Presidential Teaching Fellow, university spokeswoman Karen Wentworth told the Albuquerque Tribune.

Risso said Moy was selected by a committee of upper-level administrators from within the campuswide community.

"He just worked very, very hard at his job," she said.

The city medical examiner's office yesterday said that Moy had drowned, and that the death was accidental.

Most of Hawai'i's drownings occur in the ocean. From 2001 to 2006, there were 323 ocean drownings — 85 percent of all drownings.

The number of ocean drownings gradually increased each year from 45 in 2001 to 68 in 2005, then dropped to 59 in 2006, according to the state Department of Health.

Most, 56 percent, happen on O'ahu.

Autopsy reports of the victims from 2001 through 2004 showed that almost half — or 46 percent — had some sort of intrinsic or personal factor that contributed to the drowning, according to the Health Department.

The most common factor was circulatory disease, most often heart disease — especially among victims 50 or older.

Thirteen percent of the victims tested positive for alcohol and 16 percent tested positive for illicit drugs, according to the Health Department.

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.