Cops. When I see one in the rearview mirror, my hands automatically assume the position at 10 and 2 o'clock on the wheel. I verify my speed, check my buckle and turn down the radio. I'm a good driver, but when I see a cop, I become a nervous Nellie.

It's the same when I see a patrol boat on the water – I'm convinced I'll get pulled over. Many boaters I know feel the same way.

But after spending an afternoon on the St. Croix River on the Minnesota-Wisconsin border with the Washington County Sheriff's Department water patrol, and seeing the river from their point of view, I learned that some boaters have good reason to be concerned about getting a ticket – and some should be glad they do.

LIZ PASCHKris Stewart is one of the many marine officers keeping boaters safe.MEET THE COP

I met Deputy Jim Gribble at the Windmill Marina in Afton, Minnesota, 20 minutes southeast of St. Paul. Gribble has served with the sheriff's department since 1990, much of it in the marine patrol unit. He's been a boater as long as he can remember, but didn't always follow the rules he now enforces. His parents owned a resort in northern Minnesota, and one of his jobs was setting up the rental boats.

"I remember Dad letting me take boats out with a 3-horsepower motor when I was in second grade," he says. "I got to use the 6-horsepower when I was 10, but got caught putting four of them on a fishing boat when I was 11. I was grounded for the summer."

Gribble's early boating experience at his parents' resort included teaching water skiing when he was 12, and ski boats are just some of the many watercraft out on the St. Croix River, called "the Croix," when I rode along with him Labor Day weekend.

As we pulled out of the marina, there was a large high-performance boat in the channel. My friends with similar boats are frequently stopped for a noise level check, so I was surprised when Gribble continued driving.

"Personally, noise is not a big deal to me," he says. "I will stop boats for wake violations, people on the transom or bow or not inside the boat, or no visible registration."

HIGHS AND LOWS

As soon as he finished his sentence, we spotted a 19-foot Glastron making a visible wake in the no-wake zone. Gribble signaled the driver to stop, and we pulled alongside.

The driver, pointing to two much larger boats, said he knew he was making a wake but was trying to keep his boat under control after the passing boats had caused huge wakes. Gribble nodded and then checked his safety equipment and registration, gave the driver a warning, and gave the two PFD-clad children printed awards for wearing their life jackets. He received broad smiles and enthusiastic waves in return.

"That's one of the highlights of the job," says Gribble, waving back to the kids.

We headed downstream to the next no-wake zone at Kinnikinnic State Park. "My core concern is with the safety of everyone on the river," Gribble said, and described some of the unsafe things boaters do. He recalled one of the worst boating events he experienced while on duty in 2007, involving a PWC towing three 12-year-old girls. The driver was a novice and had also been drinking. She was trying to give the girls an exciting ride and whip them off the tube they were on. She finally managed to launch the girls into the water – less than 100 feet in front of a runabout, with four people and a two-month-old baby on board.

"The boater tried to miss the girl in the water, but could not stop in time," he explains. "The girl in the water was filleted from chest to toe. She lost almost all her blood. She survived, but has scars and a limp that will never fade."

LIZ PASCHIntoxicated boaters are taken in for booking, including fingerprinting.AN ARREST

An urgent call from the Washington County dispatcher reinforced his words. A person reportedly was thrown from a boat in Hudson and left in the water. Gribble knew from experience he might need to rescue an injured boater, and the concern on his face was evident. I hung on while he drove full-throttle to the scene several miles upriver.

We met up with Deputy Kris Stewart of Wisconsin's St. Croix County water patrol, who updated us on the situation. The two officers knew each other well, since the St. Croix River borders Minnesota and Wisconsin, where they both have jurisdiction. Stewart said he saw the boat in question pick up its passenger from the water. He also said the helmsman saw him, because the boat reversed direction and snuck around the back of the islands using a shallow channel to head upstream.

Stewart's patrol entered the main channel behind one island, while Gribble drove our boat behind another. We caught up to the boat, a 19-foot Larson, at the north end of the no-wake zone. Gribble signaled it to stop, pulled beside and tied the boats together. Even though the small boat is rated for carrying 10 passengers, we counted 12 young adults jam-packed aboard. Gribble asked for registration and identification and then conducted a safety check, which indicated an insufficient number of life jackets, a non-functioning fire extinguisher and a throwable floatation device that was not within easy reach as required by law (although it was up to Coast Guard code).

The helmsman's slurred speech prompted a field sobriety test, which was conducted while the other passengers laughed and shot pictures of their friend being handcuffed. None were capable of driving the boat, due to drinking or inexperience. The helmsman and several passengers were transferred to the patrol boat, to get the Larson back to capacity.

Gribble retied it securely to the patrol boat, and we motored slowly to a marina at the south end of the no-wake zone, nearly a mile away. Gribble had radioed ahead, so several Washington County deputies were waiting to assist. The helmsman was led in handcuffs to a squad car for transport to the county jail, while two deputies questioned the other passengers at length and cut their summer finale weekend short with an unhappy ending.

At the county jail, the boater understood the consequences of his choice and gave his full cooperation. "Operating the boat unsafely is what drew attention to me," he says. "If I wouldn't have done that, I wouldn't have been brought to jail. I don't blame anyone but myself – it was stupid."

With Gribble's responsibility completed, we returned to the marina. I watched from shore as he headed onto the river for the rest of his shift. Somehow his boat looked different to me – more like a rescue boat.