For a British journalist, knowing only the stifling urbanism of a Washington summer, the Chesapeake Bay is like another planet.

It sparkles with life. It changes one's ideas about time, about boats about American life, about fish, about weather. And it shows what a little physical distance one needs to travel from the District of Columbia to recede into a remote federal dot in the minds of men.

"Our friends in Washington," Bay people say disdainfully, and wrinkle their brows at the inability of the Food and Drug Administration to grasp, for example, that menhaden oil is perfectly edible stuff even though it was originally used in making linoluem.

They might be talking about men from Mars, by their tone, not from a city an hour's drive away. This 200-mile bay of sinuous water, teeming with crabs, jellyfish, shifting islands, remote creeks and summer thunderstorms, is a world with its own species and even its own language.

I spent three days on the bay, traveling naturally, on the water.

To reach our boat, the 45-foot Amron moored on the far shore at Cambridge, involved a sudden change of persepective in itself. There is a miniature organization, Maryland Airlines, that actually makes a living ferrying rich commuters across the bay to Washington on a scheduled daily flight.

My British ear cannot cope with the way Marylanders swallow their consonants: It sounded on the phone like "Marilyn Airlines," but I was reassured when they said: "We'll take the big plane."

They also said: "If there's a thunderstorm we won't go."

The big plane from National airport had two engines. It just held four passengers, but it was the smoothest ride I ever had, and at $18 one of the cheapest.

At the Cambridge Yacht Club, they were loading a basket of live crabs aboard the Amron at $20 -- slightly dearer than the plane ride. These crabs, tasty and vicious, were to be the focus of my waterborne life for the next 48 hours.

I came to know them intimately. For one thing, we kept them in the boat's shower, where several escaped to lurk on the floor, snapping hysterically at each other and any passing foot.

I learned how to pick them up, finger and thumb clamped nervously reound the back leg joint. I learned to recognize the tell-tale red markings that show a crab is becoming a "peeler', ready to clamber painfully out of its carapace and become a helpless, soft-shelled delicacy. So this was what I had been wolfing down in Georgetown restaurants all summer . . .

The rougher the weather, the more crabs escaped. How do you put back one crab in a basket without allowing a mass breakout by 50 others? As we steered through a freshening breeze, these questions began to seem much more interesting and important than, for example, what preciesely Jerry Ford has said to Ronald Reagan.

Crab-catching and crab-picking are a fundamental part of life on the Chesapeake Bay, but not as important as the weather. Before the crabs could go in the pot, we had to reach Solomons, 50 miles south and across the narrow bay.

The thunderstorms come up in late afternoon, and we needed to be anchored by then to ride them out. As the boat made a steady 4 knots into the choppy open water, we steered round and awesome sight.

A huge, dark stadium of cloud stretched from the sky to the water, laced with bolts of lightning. We could see a ship disappear into it, a big freighter from Baltimore ploughing out into sunlight again. It was some storm.

We missed it, or it missed us, marching off westward. As the wind rose to 30 m.p.h., we rode the waves, sitting perched on the bowsprit, plunging up and down, giving cowboy yells, drenched in glittering spray.

"Boys will be boys," said our skipper dourly, in the tones of a man hardened by too many dogs and children on vacation charters. "A better ride than Coney Island," we shouted over the waves.

These sea trips are unpredictable. Just as we anchored, anxious to come to grips with crabs, the cruiser was finally engulfed by a storm.

Even in a sheltered inlet, the anchor was dragging. Battened down with the crabs, unable to cook them, we winced at the hurricane gusts singing through the rigging. The sea turned into a crazed spin-dryer of rain and spray.

Lightning bolts cracked and banged by the dozen, and deafening thunderclaps burst around and overhead. Just as the storm seemed to be rolling away, another squall blasted down the water and hit the boat. Tiny balls of ice, from heaven knew what altitude, screamed into the wheelhouse.

It felt as though a tornado had touched down. Later, much later after the storm quietened, leaving only a silent lightshow of electricity to play around the horizon, that turned out to have been exactly what had happened.

For on shore, reached by rubber dinghy, there were scenes of considerable havoc. Trees had been ripped down, leaving 10-foot splintered stumps like an old photograph of a World War I artillery barrage at Verdun. s

Small boats had been sunk at their morrings; corrugated iron roofs and walls had been opened like cans, concertinaed and flung through the air. The power lines were down, TV antennae crazily bent.

By late that night, under the stars with the rain pattering down, the air, cooled at least 20 degrees, was already beginning its climb back into the summer 90s.

Before we finally consummated relationships with the blue Atlantic crab, we had to travel 50 miles through a thunderstorm to Solomons. Then it began.

We had one small steaming pot, and tossed them in by twos and threes with pepper sauce. They clambered out and were focefully crammed back.

They came out hot and scarlet. Off went the swimming legs that enable them to dash and hover like helicopters. Off came the breast-plate, the gray "dead men's fingers" of the lungs, and the brown visceral goo.

The big juicy claws crack neatly with a sharp crevices of the body, packed with succulent meat, torment the ametuer. Stories were exchanged of the professional crab pickers, filling cans in minutes with tireless flying fingers, artists of the bay.

The first couple of dozen crabs were consumed traditionally with ice-cold beer. As the night wore one, we switched to rum and synthetic pina coloada mix.

Below decks, the dimly lit Amron filled with steam, and shirtless figures, sweating in the semidarkness, crouched over pots and over the mounting pile of discarded and mutilated crab remains. It was a Dantean scene such as crab mothers might have described to frighten their children.

They were delicious. So were the crab omelettes for breakfast, and the crab cakes for supper. There was some slightly hysterical talk by now of making up crab cocktails and crab sundaes.

But we sailed off in search of the final truth about another inhabitant of this prolific, ecologically subtle bay -- the menhaden. Nobody eats the menhaden in Georgetown restaurants. But turkeys and chickens know it well. So do the felines who banquet off Huff and Puff cat food.

Out quest was even further south, past the euphonious mouths of the Piankatank and the Susquehanna, to where the Potomac sprawls into the bay, and to just inside the Virginia line.

It took us on another small tour of this complicated 4,000-mile coastline, a real estate agent's delight, where every house can have its acres of waterfront and grand mansions may be hidden from the land but sweep down in neat lawns to their own stretch of sea.

We were heading for Reedville, a town of which few Americans seem to have heard. It is certainly nothing much from the land: one street of pleasant clapboard houses on a road that simply gives up and stops.

By water, it at first looks peaceful, slipping on quiet gray day into the estuary of the Great Wicomico River. On a red steel buoy out in the water nest a trio of ospreys. Their constructions teeter untidily, bouncing around on the summit.

Jellyfish, the bane of Chesapeake Bay, flit by on the current in squads, with pale, trailing arms. And the horizon is dotted with stakes: the watermen of the bay do not just put down hundreds of square crab pots; they also build elaborate fish ponds everywhere in the shallow waters.

We dock at a tiny marina with a sandy beach. It seems remote and leisurely. A 50-foot sailing boat bollows us in: "I'm going to Newfoundland," its master says. "I'm just going to play. So long as I'm back by October."

But with a head full of these idylls, Reedville from the sea turns out to be a shock. Round the creek stretches an alarming industrial scene.

There are crumbling, abandoned wharves everywhere. And behind them in the fading evening light, tank farms, factories, refineries and docks line both sides of the shore.

Huge clouds of white vapor smear across the inlet, blurring endless rows of lights from the former naval supply ships, tying up, unloading, putting out again, round the clock.

As the dawn breaks, flights of single-engined planes roar off over our heads into the bay. They look as if they are taking off from an aircraft carrier in the first reel of a grainy war film, and not from the grass strip the pilots call "Reedville International Airport."

The purse-seine boats steam out in file behind them, outlined in their drab blue paint against the flat horizon, each with a stubby crow's-nest, to look out for fish on days the spotter planes fail them.

A pilot, frequently a retired captain, is at the helm. And when the captains become too arthritic for that, they can be seen mending nets in their old age. They live by menhaden all their lives. b

In the early mornings, the working captains are snoring below, saving their strength for later. One of the plant-managers comes aboard the Amron and talks to us about menhaden. They are a toothless, bony, greasy cousin of the herring, and they come by the thousand-million.

Last year, nearly a billion were hauled out of the bay, spotted by the little planes dipping like gulls and fought over by the competing captains, who with their crews, work strictly on commission. A captain make $700 on a good day in the six-month season, a raw deckhand perhaps $125.

The fish are tipped on the spot into steam vats, squashed flat into "presscake," and dried into a brown flour, which is 60 percent protein. The oil is refined separately and so is the water residue, into a high-protein cream, which the makers try to persuade farmer to feed to their calves.

This side of the Chesapeake Bay is big business.

Over all of it hangs a revolting, gluey, fishy smell. "People don't exactly like it," says the plant manager "but when they smell it, they don't smell fish -- they smell money."

For an outsider, this, too, is an interesting discovery.

The Chesapeake Bay is not just a delightful corner of the world in which to indulge a piece of Washington escapism. It is a working environment. There is enough to buy and sell, to hunt and haul and process and transport, to make a distinct life style for thousands of people.

And I never knew any of it existed.