A flock of cormorants skittered along in front of our small motorboat in a black V, dipping and rising just above the river.

Hank Snyder, a National Park Service research specialist, laughed a little because I was surprised to see them so close to the city. But then, the Potomac, our hometown river, always offers a fresh perspective on everything: on something as familiar as National Airport or a scrap from history or cormorants. Sometimes it gives you an unplanned face-off with nature herself, a truly humbling experience.

Of the predictable aspects of the river, the sweetest is how quickly it lets you escape the city.

The cormorants were less than two miles below the Wilson Bridge; on land we'd still have been eave-to-eave in houses, but on the river we were close to the Maryland shore in the marked deep water channel that runs to the Chesapeake Bay.

The Potomac is more than a mile across at that point, but we had it pretty much to ourselves. Trees climbing the steep shore were so thick that the haze took on a greenish cast and the few houses we could see were more curious than intrusive.

Occasionally, a sunbeam sneaked through the haze to dance on the river and, here and there, a creek split the bank and joined our journey down toward Mount Vernon. It was a day for sensory overload.

Still smiling, Snyder pointed toward Virginia and shouted over the engine, "More than 250 different bird species have been spotted over there in Dyke Marsh." The marsh is a 240-acre wetland preserve that's typical of the Potomac's estuary.

Most of the land along the river in the metropolitan area, 96 percent of it inside the Beltway, is publicly owned or under a scenic easement.

We have history to thank for that. The Potomac is hip- deep in it, and every creek, cove and point of land on this reach seems to have played a bit part.

Snyder knows the river and its history and enjoys sharing it. He talked about the sacred Indian ossuary, the swirling currents behind Mockley Point and, as we came under the gray-blue walls of Fort Washington, about the star forts built along the river during the Civil War.

Fort Foote and Fort Ward, both in Maryland, had been hidden by the foliage, but Fort Washington sits on a point where the river and Piscataway Creek meet.

Inside, the fort is stern and military, but it's softer, less hostile from the river despite its size. Age and weathering have gentled the native Occoquan stone of its walls and, backed by the rolling Maryland hills, the fort seems -- well, neighborly.

Mount Vernon, only a mile or so downstream, is much more imposing: square white columns and neat, open lawn rolling down to the river.

When the estate was built, the Potomac was both country lane and intercontinental highway, abustle with neighbors visiting by skiff and ferry and with ocean-sailing ships delivering goods from the Continent and picking up local tobacco and lumber. The large river plantations had river docks, and Alexandria and Georgetown were flourishing, rival seaports.

George Washington loved the Potomac and brought us all here to its banks. Helped by Jefferson, Madison and Adams, he lobbied Congress for seven years to have the capital city built on this river.

His reasons lay as much in geography as in politics: At the time, the Potomac valley was the most direct route from the Atlantic to the Appalachians and, beyond them, to the Ohio valley and the heart of the continent.

From a spring on Backbone Mountain in West Virginia, the main stem of the Potomac flows nearly 400 miles to the Chesapeake Bay, and its tributaries reach into four states: Maryland, Virginia, West Virginia and Pennsylvania.

Most important, as Frederick Gutheim points out in his book Potomac, the Potomac valley formed a relatively easy, natural route for men to follow in their search for a way west. For 200 years, they did just that.

Europeans may have explored the Potomac as early as the 16th century. At least one Spanish map shows it, calling it the San Pedro.

John Smith, though, was the first to give us a written report. He and a crew of 12 from Jamestown explored it to the head of the tide at Little Falls in 1608. They hoped to find gold, but it would be more than 250 years before gold would be found near Great Falls.

Smith also named the river, adopting a word which local Indians applied to the site of the present city.

The Indians, according to Smith and others, were highly skilled traders, friendly and peaceful until the white man pushed them out of the valley.

There are as many interpretations of the word Potomac as there are historic spellings, but the U.S. Geological Survey uses one which seems most fitting: "the place to which tribute is brought."

Washington was convinced that the Potomac, "by its inland navigation," would be the vital link binding the new settlements across the mountains to the Union. He called the river "the centre of the Union" and, geographically, it was.

Under the circumstances, where else would he put the new Federal City?

Washington believed so strongly in the Potomac valley route to the west that he invested in the Potowmack Canal Company, which tried, from 1784 to 1828, to improve navigation above the fall line by building canals around such major obstacles as Great Falls.

The incline plane from the Great Falls canal and the iron eyebolts that carried hawsers for the barges can still be seen from the river below Great Falls.

The Potowmack Canal was followed in 1825 by the C&O Canal, which runs parallel to the river all the way to Hancock. The C&O eventually gave way to the railroad, and the Potomac faded from national consciousness.

You can still get a sense of the intimate relationship between the city and its river from the water: a hint, anyway, of L'Enfant's grand design, in which major buildings were oriented toward the Potomac or the Eastern Branch (the Anacostia).

For instance, where the Anacostia and Potomac meet and the Army War College guards the city, the Capitol dome can be seen in the background atop Jenkins Hill.

With a little imagination, you can see the scene as L'Enfant planned it, with a 40-foot waterfall "issuing from under the base of the Congress Building" into Tiber Creek and into the Potomac, about where the Tidal Basin is today.

As the city has changed, so has the river. It has been dredged and quarried, polluted and scrubbed up, overfished and, from Georgetown to the Anacostia, landfilled and walled so that it is half its former width.

Any place along the river (except at Greenleaf Point) where the land levels off less than 50 feet above water level is man-made. You can bet the mortgage money on it.

The waterfront, though, is pleasant, clean and downright pretty from water level, and still full of surprises such as the fleet of landing craft moored in Alexandria just above the Wilson Bridge; and the former presidential yacht Williamsburg, moored at Blue Plains and those beautiful boats docked in the Washington Channel.

Hidden in a cove above Georgetown, near the Three Sisters Islands, is the wreck of a metal dinghy with the name Wendy still visible.

A little farther upstream, at the base of the Virginia palisades, an old blast box and donkey engine can be seen at low tide during this low-water time of the year. They were used in the quarrying operation that left the straight angular cuts in the palisades rock.

Today, the river is more barrier than binder, as anyone who crosses it at rush hour knows. Yet it's still vital to us as a source of water, about 450 million gallons per day.

It's just as important, in a more subtle way, as a park, playground and sports complex, kind of a natural, historic theme park, and it's still relatively undiscovered and uncrowded.

Wildlife flourishes along the river, as Charlie Taylor, a professional fishing guide who's out on the river early in the morning, can tell you. He has seen deer leap into the river ahead of his boat and swim across to an island. Once, a couple of years ago, he saw a black bear rambling up one of the runs below Chain Bridge.

I've seen raccoon cleaning fresh-water clams at river's edge, as wll as muskrat and green and blue heron, osprey and kingfishers. Others have glimpsed red and gray fox, lynx and working beaver, not to mention the seemingly endless variety of birds.

The great schools of fish once caught and shipped from the Potomac by the hundred thousand pounds are gone, but there are fish here for the sportsman: shad, bluefish, perch, large- and small-mouth bass, catfish and carp, to name a few.

Charlie Taylor says, "Of all the rivers I have fished, from Florida to New Hampshire, the Potomac is the best."

This wide variety of fish, bird and plant life results from Washington's position just below Little Falls, where fresh and estuary water meet, making the lower Potomac both mountain river and tidal estuary.

The river's duality also allows for diversity in boating. Within a few miles of Washington, you can plunge through nerve-tingling rapids inside a soaring 200-foot gorge or sail all day on a tidal river. You can cruise or crew, row or race, go water skiing or board sailing or touring.

The Potomac isn't always calm and picturesque, however. Several times in this century, it has rebelled against its confines, jumped the seawall and reclaimed its own.

The worst flood of the century was in March, 1936 and it drove the Little Falls river gauge to 28 feet. Ten feet is flood stage.

In 1972, after Hurricane Agnes made two passes over us, the gauge at Little Falls hit 22 feet. Normal is between three and six feet.

Even when the Potomac is "normal," it's both squally and flashy. That means that at certain times of the year violent thunderstorms with high winds can come up without warning and the water in the river can rise very fast after any storm.

At such times, it's best to leave the Potomac to the Potomac and turn instead to one of the books that tell its history.

Three of the best are: The River and the Rocks, USGS Bulletin 1471; Potomac by Frederick Gutheim and This Was Potomac River by Frederick Tilp.

Tilp's book gives a history of every creek, cove and island on the tidal river, as well as bridges, towns and wars, past and present.

Careful, though -- Potomac fever can be catching.