Forty-one-year-old Joe Joyce of Flagstaff drowned while trying to launch his fishing boat Friday afternoon at Roosevelt Lake.
Joyce, who was camping with his 10-year-old son at Cholla Bay, is the first person to drown at the lake in three years.
Joyce and his son launched the 14-foot-long boat but couldn't get the motor started, Gila County Sheriff's dive-team specialist Sgt. Terry Hudgens said.
"He probably got out of the boat, lost hold of it and it started to drift with his son in it," Hudgens said. "He went swimming after it and went down about 50 yards off shore."
When Joyce began to flounder, witnesses went to help, but were unable to save him, deputies said.
"Other people on the beach brought the boat back in, took the son under their wing and called us," Hudgens said.
Joyce slipped below the surface shortly before 4 p.m. Divers found his body at 6:20 that evening in nearly 15 feet of water.
"We don't really know what caused him to drown," Hudgens said. "He really hadn't gone far enough for that kind of fatigue."
Gila County Sheriff's Sgt. John Holmes, who is stationed out of the department's Roosevelt substation, said Joyce may have succumbed to hypothermia.
"The water is about 54 degrees," he said. "The average water temperature in the summer is about 72 degrees, and that can be hard to take."
Holmes warned that "any time you're on the water, make sure you're wearing a personal flotation device."