Napa County sheriff’s deputies continued searching the surface of Lake Berryessa on Tuesday for signs of a missing Glen Ellen man who was knocked from his speedboat Saturday.

Sheriff’s Capt. Doug Pike said deputies on a sheriff’s boat were looking for the man, who is presumed dead.

Roger “Deets” Winslow, 49, a longtime Sonoma Valley High School wrestling coach and father of three, apparently was jolted from his high-speed performance boat while on a cruise with two friends.

Deputies still plan to conduct a more thorough search of the lake bottom, if necessary, and are hoping to borrow an unmanned robot from the Santa Clara Sheriff’s Office, which can travel deep under the water.

Napa County’s robot wasn’t capable of reaching the deeper sections of the lake floor, officials said.

The investigation into what caused the incident, including whether the dual-engine racing boat with a pickle-fork nose had a mechanical failure, remained ongoing.

Winslow, who was driving, apparently was thrown overboard and then hit by the propeller when the boat rocked first one way then jolted another.