Sgt. Ronald Wilkins of the D.C. Harbor Patrol has a beat that indisputably is the wettest in the city: six square miles of the Potomac and Anacostia rivers and 42 miles of shoreline.

On a recent sweltering Saturday, the sergeant squinted down the river and spotted his quarry. He steered his patrol boat smoothly alongside a couple, legs entwined, heads tilted to the sun, their inflatable boat rotating in blissful little eddies.

They eyed him as warily as if they'd just run a red light. The truth was out--they had no life preservers, and gently, politely, he ordered them back to the nearby shore.

Wilkins steered away. "Mean old police again," he said with a philosophical smile. He said he is a stickler about life preservers: It's against the law to be in a boat without them.

But for the most part, as he glided, zipped and twisted down the Potomac, issuing a warning here, a suggestion there, he tried to keep things light.

His beat has been around since the city force was formally founded in 1861, although Harbor Patrol was a one-man operation then. Now a branch of the D.C. Police Special Operations Division, it has been expanded to 20 officers, three sergeants, a lieutenant and a clerk, but its function is essentially the same.

"They are much more service-oriented than they are enforcement-oriented," says Deputy Chief John C. Connor, SOD commander. "They do issue some tickets but those who receive tickets have to be very flagrant violators."

Although the officers carry guns, wear badges and patrol in seven powerboats, they don't make many arrests, according to Lt. James L. Hampton, harbor master. Last year they made several arrests for such things as disorderly conduct and operating a boat under the influence of alcohol.

"A lot of people think they're not performing police duties, but they do save lives and respond to disasters," says D.C. Police Chief Maurice T. Turner, who says Harbor Patrol officers received 20 to 30 citizen commendations for their work after a sudden freak squall capsized dozens of boats last spring.

"They're very skilled," Turner says. "They sometimes have some very dirty work to do, picking up bodies of floaters."

Last year the Harbor Patrol helped pull 94 bodies out of the water, a figure higher than usual because of the Jan. 13 Air Florida plane crash at the 14th Street bridge, in which 78 people were killed. Within the first seven months of this year, they recovered nine bodies.

Most of their work involves rescuing people from hazardous situations, including capsized boats. Nearly 600 persons were rescued last year and about 250 so far this year. Many people "just buy a boat and head on down the river," ignorant of boating safety rules, says Officer Jim Quigley. "These are the people we wind up rescuing most of the time."

On a typical day, they patrol from 7 a.m. until 11 p.m. and remain on call throughout the night. Besides rescuing troubled boaters and towing disabled crafts, spot-checking vessels for safety violations and slowing down speeders, they investigate accidents and register all D.C. boats.

For the recreational visitors to the region's miles of waterways, "this is kind of an outlet," says Wilkins, a 19-year D.C. police veteran who has spent the last dozen on the river. He sympathizes with water enthusiasts: "They hassle with a job and traffic, and maybe get a traffic ticket on the way over, and they finally get to a boat--their sanctuary. And lo and behold, out here on the water, here come the police again!"

In some situations, a low-key, democratic approach to handling problems seems to work best. Take the time Wilkins noticed a big crowd forming on an unusually large group of anchored boats and thought immediately that something was wrong. For one thing, the crowd was watching him, and then glancing quickly at something else, their eyes going back and forth so many times they looked like an audience at a tennis match.

Finally a boat emerged majestically from the group. "This guy comes along with his wife or his girlfriend sitting up in the bow like a hood ornament, with no top on, just as proud as a peacock," recalls Wilkins, who stopped the boat.

The crowd began booing, but they were clearly of two minds: "Some were saying thumbs down, give her a ticket, and some were saying thumbs up, let her go," Wilkins says. Ultimately, he gave her a warning and she put her top back on. He says he wanted to avoid an "ugly scene." And "it looked like there were more people on her side anyway."

While the officers seem to have their share of light duty, there's a flip side, too.

"A lot of people think it's a gravy job down here, and it is a very good job," Quigley said. "On a nice day like this, it's beautiful, and then you have your cold winter nights and your 50 mile-an-hour gusts blowing, and you get a report of someone jumping off Chain Bridge."

In an emergency, the Harbor Patrol will leave its waters and assist the Coast Guard or Maryland Natural Resources Police, who patrol nearby and do the same for them.

"One time a next-door neighbor drowned and it was several days before we found him," recalls Corp. John Furey of the Maryland police. "That was a particularly hard job, to bag up my neighbor, and they came down to help."

They're a "pretty gung-ho bunch," with "probably better morale than most police agencies," Furey says.

After awhile, the harbor police come to know the regulars on the waterways.

"A lot of people wave at you as you go by," says Wilkins. "You feel like a small-town sheriff . . . . almost like 'Mayberry RFD' or something."

"The people on the river are more friendly than on the street," agrees Officer Lila FitzGerald, who joined the Harbor Patrol just over a year ago and is the only woman officer there.

Making friends is just one byproduct of working in the Harbor Patrol, however.

"It's a job where you've really got to be a boater as well as a policeman," Quigley says. "It combines the best of two worlds."