A Windham man was rescued from Sebago Lake Sunday afternoon after falling into open water driving an all-terrain vehicle across the lake.

Allen Hooper, 71, was pulled off some rocks about 60 yards from shore by officers of the Cumberland County Sheriff’s Office and Maine Warden Service in an airboat.

Hooper was driving a “side-by-side” ATV on the frozen lake around 1:30 p.m. when he hit unexpected open water. He swam about 30 feet to the rocks, the sheriff’s office said in a press release. Hooper was the only passenger in the vehicle and was unharmed but hypothermic.

A nearby resident on Bridges Lane in Raymond witnessed the crash and called emergency responders. Hooper may not have survived without the call, the sheriff’s office said. The air temperature on Sunday afternoon was about 22 degrees with a light wind, and the rocks Hooper was on were surrounded by mostly open water, making swimming to shore a challenge.

“Had this resident not noticed Hooper unknowingly drive into open water, his survival would have been questionable,” the sheriff’s office said.

The airboat used to rescue Hooper was on loan from the town of Harpswell for the annual Sebago Lake ice fishing derby held over the weekend.

It was the second such incident on the lake in two days.

Two people escaped injury Friday night when their side-by-side ATV went through the ice on Sebago Lake. The pair were headed to an ice shack when they broke through the surface. Rescue workers assisted them off the ice, a police dispatcher said.