A North Idaho teenager pulled from the bottom of an old mill pond Wednesday remained in critical condition Thursday at Providence Sacred Heart Medical Center in Spokane.

August (A.J.) Marksworth, 16, of Spirit Lake, was found unconscious in water about eight feet deep 5 to 10 minutes after he slipped under the surface of the lake’s mill pond late Wednesday afternoon.

He and a friend, Nathan Thiers, 15, also of Spirit Lake, had been wading in the water when Marksworth stepped into a deep spot, the Kootenai County Sheriff’s Departmentsaid. The teen is not a good swimmer and can’t tread water, family members told deputies.

Thiers tried to pull Marksworth to shallower water, but both became tired and let go of each other. Marksworth then sank to the bottom, the Sheriff’s Department said.

Marine Deputy Bob Bjelland, a former Navy diver, was flagged down soon after the incident and had a private boat take him out to the scene. Within minutes he brought Marksworth to the surface, with the assistance of a boat from Northern Lakes Fire District and bystanders.

“I wish I was 10 minutes earlier,” Bjelland said.

Marksworth was on a ventilator in intensive care as of Thursday afternoon, the Sheriff’s Department said.

Any type of water can be dangerous, Bjelland warned. “You never know what hazards are under there.”

“Wear a life jacket, learn to swim. Very simple,” he added.