The scene could be clipped from an album of American leisure dreams a trim, bright blue power boat speeds across the lapping waves of the Severn River on a hot summer Sunday afternoon, four laughing friends perched on the seats.

The beer is cold, the muggy, smog-drenched city is miles and miles behind, and the tempests of urban jobs and suburban families have been swept beneath a wide, clear, blue carpet.

But something is wrong. The boat operator glances back into the wake of the boat, blinks, looks again, then, with a glazed rueful smile at his friends, cuts off the inboard engine.

He has been driving the boat recklessly. To his surprise, he has been stopped by a Natural Resources Police officer, who will issue him a citation.

The blue boat's operator is just one of thousands and thousands of people who crowd their powerboats, cabin cruisers, sailboats and yachts onto Maryland waterways on summer weekends, and proceed to ignore even simple safety precautions they might observe on highways. Largely a result of such carelessness, 15 persons have died in water recreational accidents this year.

On recent weekends, more than 1,000 boats have crowded into several square miles of water at the mouth of the Severn near Annapolis alone, according to Sgt. Franklin Wood of the Natural Resources police.

If boat registrations are any indication, that kind of traffic is only likely to grow worse in the years ahead.

In 1968, according to police figures, the number of recreational boats registered to operate on Maryland waters stood at 66,655. By 1974, the number had ballooned to 113,748. And in 1977, the last year for which figures are available, 134,897 boats could have conceivably descended on rivers and lakes on summer weekends.

Meanwhile, faster and faster speedboats have been appearing on the market, including "jet" boats - equipped with drag-racing-style gasoline engines - that can reach speed of 100 miles an hour on the water.

No experience, knowledge, age or training is required to take such boats out onto the water - only an $18 state license. Speed limits exist only in docking areas and small creeks that branch from the main rivers.

Consequently, on summer afternoons, the Severn River and other waterways often come to resemble nightmarish waterborne fusions of a city rush hour and the Indianapolis 500 - with no stoplights or marked lanes, widely ignored right of ways, and very few police.

On a recent Sunday, Wood was the only police officer patrolling the Severn River area. Only 85 officers are assigned to active patrol of Maryland waters, and many summer days and nights, Wood says, pass on the Severn and other rivers without a single appearance of a Natural Resources whaler or patrol cruiser.

As Wood manuvered his light, 16-foot patrol boat into the severn from the Annapolis city dock shortly before noon, dozens of areas seemed to demand attention.

Fast powerboats could be seen threading through jumbled patterns of sailboats. Large cruisers churned past small skiffs, creating huge wakes that threw the small boats off course. Speedboats towing waterskiers cut through creeks ares with 8-miles-an-hour speed limits.

Nevertheless, Wood was occupied most of the afternoon in the harbor, stopping dozens of boaters who, largely out of ignorance, had failed to display the proper registration on their boats or stock required safety items.

All motorboats are required by law to display serial numbers and stickers on both sides of the hull, and carry a fire extinguisher, a life preserver cushion, a warning horn or whistle and a life preserver vest for each person on board.

Wood's absorption in stopping these minor trespassers, he said, was like that of a state highway trooper who drives out to patrol the interstate and finds that one out of every four cars does not even have license plates.

"We have to work on a very primitive level still," he said. "So many of these people don't even bother to figure out what the rules are, much less learn how to follow safe procedures."

"I've seen people who have never been in a boat before take $150,000 yachts out of the harbor," says Wood. "And I've seen them run aground five minutes later because they don't even know how to follow the channel buoys."

Wood has also seen much more terrifying fatalities have occurred in the past month, and several of the worst accidents have been in Wood's district, which extends from the Chesapeake Bay Bridge to Deale, about 15 miles south.

In all, more than 70 water accidents have occurred so far this year, according to police statistics. There were 218 accidents last year, and a total of 30 injuries requiring medical attention, including 19 deaths, according to police.

Two of the worst accidents this year occurred on the night of June 24 in the Severn and South rivers.

Around 9 p.m., Natural Resources police say, a motoboat collided with a sailboat that was using an auxillary engine. The motor boat skidded along the side of the sailboat deck, and one man on the sailboat was struck and lost an eye, police said.

Then, around 9:30 p.m., two cabin-cruisers collided near the mouth of the Severn River, police said. One of the boats tore over the top of the other, police said, killing one person and injuring seven others.

Police say charges have been filed against the operators of both boats in the first incident, and investigation is continuing in the cabin-cruiser collision.

If such accidents, and the Congestion problems on rivers near Chesapeake Bay are ever to be cleared up, Wood said, the state has to "make some hard choices."

"Either we have to have speed limits and required training for boaters, and more personnel to enforce the law, or we have to watch these problems - and the accidents - keep rising," Wood said.

"These people don't like to be infringed on when they've involved in recreational activities," Wood said. "But someone has got to ensure that the waterways are safe to go out on."