The body of the 24-year-old victim from Mountainside Avenue was found in 15 feet of water shortly before 3 p.m. He wasn't immediately identified by name.
The boarder had lost his grip and fell into Dators Pond at the foot of Stag Hill Road early Thursday evening, responders said.
His older brother then paddled to shore shouting for someone to call 911, Mayor Jim Wysocki said.
The first responder, Mahwah Police Officer Travis Canning, headed into the pond just west of the Ramapo River off Routes 202 and Route 287 near the Rockland County border, less than a mile from the victim's home.
He was followed by Officers Dan Stewart and Michael Silano.
Several dive teams arrived soon after.
The Mahwah Fire Co. 1 Dive Team was joined by colleagues from Fair Lawn, Lyndhurst, Wallington, Wyckoff, Oradell and Ringwood, as well as divers from Piermont, Stony Point, Thiells and Parsippany.
Mutual aid also was provided by firefighters from Elmwood Park, Suffern and Tallman, along with Mahwah EMS and DPW and the Bergen County Sheriff's Office.
A police drone was sent up, but there was no immediate sign of him in a lake that is 60 feet deep in some areas, he said.
Also working against rescuers using sonar were weeds and debris, including two vehicles, responders said.
It was the second drowning of a young man in a lake in Mahwah in less than a week.
A Hudson County man who didn't know how to swim drowned at a lake in nearby Darlington County Park last Thursday despite an intense effort by rescuers to save him.
SEE: Hudson Drowning Victim, 21, At Mahwah Lake Didn't Know How To Swim
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