Sonoma County Sheriff's Sgt. Ed Hoener picked up the binoculars and stood up from the passenger seat of a marine unit patrol boat humming along the green-blue water of Lake Sonoma.
"He's on the gunnel" said Hoener, referring to the side of the boat, a perch illegal on a moving vessel in California.
Behind the wheel of the patrol vessel, Deputy Matt Parlato steered them toward the boaters.
"It sounds ticky tack, but every stop we make can prevent a tragedy," Parlato said of the enforcement effort.
Two sheriff's marine units spent extra hours patrolling Lake Sonoma's waters during the weekend, part of a nationwide crackdown on drunken boaters called Operation Dry Water.
And though most of the enforcement stops on Lake Sonoma Sunday involved life jackets and fire extinguishers, each stop becomes a reminder for boaters to be careful, Hoener said.
The man who had been perched on the gunnel slid into a seat as the sheriff's boat neared and Hoener called out to them.
"What you can start doing is start making sure everyone has a life jacket in their hands," Hoener said.
One child in the boat was snug in a vest, however the group was short a few floatation devices for the adults and also lacked a fire extinguisher and floatation cushion required for the driver.
Hoener gave them two options: "go up to the marina and buy life jackets and a fire extinguisher, or let some people off the boat," he said.
Parlato handed Santa Rosa contractor Ron Smith a pamphlet on boating safety.
"It's nice to be educated, now we know," said his wife, Lisa Smith.
Lake Sonoma's 2,700 acres of surface water and 50 miles of shoreline draw flotillas of boaters, kayakers and swimmers to the area during hot summer days.
The sheriff's marine unit patrols the lake as well as the Russian and Petaluma rivers, the coastline, Bodega Bay, Sonoma Creek and a portion of the San Pablo Bay.
The unit runs on grant funding from the State Department of Boating and Waterways and is also on contract with the U.S. Army Corps of Engineers, which controls the reservoir.
Most arrests involve alcohol use, Hoener said. The same laws that apply to vehicle drivers and intoxication apply on the water.
On Sunday, Hoener gave the Smiths a warning but no ticket. "I let them off easy," he said.
Deputies later arrested four people on misdemeanor alcohol charges, including three passengers and a driver, all in the same boat and all from Cloverdale.
Another man was arrested after he jumped from the bridge spanning the lake near the marina, Hoener said. The team also issued eight citations for various boating and safety violations.
Back on the water, up the Warm Springs arm of the lake, Parlato saw a child swimming toward the back of a boat while the motor, and propeller, remained engaged. He yelled at the driver to cut the engine.
They headed toward the Dry Creek arm of the lake, passing Deputies Dan Peccorini and Tom Galovich.
"Hey, there's a party group behind rattlesnake Island," he said. "Check them out."
California boating regulations can be found at www.dbw.ca.gov.