WE started the 44-mile trip up the Potomac River in Stafford County, hearing news of healthy crab catches at the mouth of Aquia Creek from Nathan and Charles Bourne as they hauled up pots filled with dozens of the beautiful swimmers.

We finished it five hours later at the Columbia Island Marina near the Pentagon, where a lone sunbather on a raft was wrapped in humidity and the roar of traffic beside the river and airplanes above. In between, we took in sights from a cruise boat full of tourists at George Washington's Mount Vernon to the exposed hulls of World War I transports sunk, but never quite disposed of, at a spot called Mallard's Bay.

The point of the trip in a small Boston Whaler by two senior Chesapeake Bay Foundation staffers was to check on the health of the river north to Washington.

They also wanted to witness how sections of the Potomac upriver are different from what's along the shorelines here.

The most dramatic thing predicted and delivered by the skipper, senior CBF naturalist Bill Portlock--how rapidly things would change in the stretch near Washington.

At Mount Vernon, both sides of the river were pristine and green, with a barn or two and Washington's home the only things in contrasting colors.

But round one river bend and cruise a few miles beyond and suddenly you see the trappings of a bustling city all around--high-rise apartment buildings, hotels, a big shopping center and more, more, more.

The Washington Monument, the Capitol and iconic buildings like the Torpedo Factory are visible just up the way.

Grasses the difference

One huge difference between the river at our start and finish was water clarity.

Portlock and fellow CBF staffer Chuck Epes measured that in the midst of thick underwater grass beds extending from Aquia Creek into the river.

In these beds, which Portlock identified as celery, coontail, hydrilla and other grasses, which help to settle out particulates, a simple visual device on a string found visibility to 61/2 feet.