Open daily, 11:30 a.m. weekdays, until 3 a.m. weekends. No credit cards. No reservations.

Food: Seafood, less reliable than the tides

Style: Casual, service sometimes excesively casual

Price: Moderate, main dishes averaging $4.50

ONE OF THE ANSWERS that Washington eaters always have ready in case anybody should ask them what kind of restaurant Washington needs more of is Good Seafood Restaurants. Not all of those people lining up to cross the Bay Bridge on weekends are doing so for the sand and ocean. Clams, crabs and rockfish have their own magnetic force.

At last someone noticed. Au Pied de Cochon, the heavily patronized brasserie at the corner of Wisconsin Avenue and Dumbarton Street, spawned Aux Fruits de Mer two doors down Wisconsin. Tropical fish swim in the window in case you don't read French. And the menu at the door lists over forty seafood dishes with not a meat among them. Seafood fried, seafood broiled, seafood baked. Seafood in salad, seafood in sauces, seafood in sandwiches. Nothing costing more than $5.50. A seafood cafe.

One should understand from the start that this is not [WORD ILLEGIBLE] Eastern Shore sort of seafood restaurant. There are no [WORD ILLEGIBLE] shell crabs or crab chowder. It is a French seafood cafe and, like the furnishings of Holiday Inns, the menus of French cafes in this country are similar whether they are in Sioux City or Bangor. Thus, predictably, Aux Fruits de Mer serves omelets, quiches and crepes, salade nicoise and steamed mussels. Its desserts are chocolate mousse, creme caramel and the usual pastries, the standards donw in a standard fashion. The seafoods may be nantua or white wine-sauced, or sauteed with garlic and butter. The concessions made to local tastes - fried seafood, crab dishes and coleslaw - it maked grudgingly, prepares indifferently.

Enough theory. Here is the way it works in practice. Rockfish bonne femme is, of course, French, being bathed in a creamy white wine sauce with mushrooms and tiny shrimps. A good job, the fish fresh and still moist, the sauce light and frothy, well laced with black pepper, yet still subtle. On the local side, the crab cakes could have been delightful, since the crab was lightly tossed with little besides mayonnaise, parsley and, perhaps, horseradish. But the crab was frozen Alaskan king crab, an unpardonable error among local crab cake fanciers, and the same frozen crab showed up in the omelet, which was further degraded by being overcooked so it was dry as well as bland.

Those are major errors, buying frozen crab instead of fresh, as well as serving hard, dry frozen French fries. On the other hand, the fish filets we tasted were fresh, and the dishes we chose from the handwritten diaily specials were carefully cooked and sauced with zest, from the scallops in a thyme-and-pepper-flecked tomato sauce to the creamy platter of rockfish.

Straying into the printed menu led us into a minefield of crucial mistakes. You can't easily fail with oysters on the half shell, except by opening them too soon or washing them; the only real flaw with the oysters at Aux Fruits de Mer was that they were small, but hey gave us seven to compensate. Clams casino, like stuffed mussels, were deliciously doused in garlicparsley butter, the clams with a bit of bacon on top. Similar though they were, and both nicely cooked, the mussels were inedible because the sand shot through them threatened our teeth. French fish soup can be a grand dish and might have been here; it was fennel scented, coral colored like the broth from bouillabaisse, and floated a slice of toasted French bread rubbed with garlic and oil. But, as an old legend went, the cook must have added another cup of water whenever another diner showed up. The wonderful flavors whimpered in the watery broth. As for the fried seafoods, the fine fish breading was laid on with too heavy a hand, and good timing in the frying hardly made up for the greasy results.

Almost good. Sometimes good. So it was with the service, too. A happy, helpful waiter one day, who took pleasure in serving us. And then indifference, a waiter we had to fetch when we wanted wine, dessert, the check. Having heard complaints that service edged into insolence, we, too, found waiters whose minds may have been on the novels they were writing, and served us as if our requests were intrusions on their important thoughts.

Aux Fruits de Mer is small and decorated with a nautical touch which stops short of being cute. It is a nice place to eat if you don't expect too much - and reasonable if you order right. For the chewy omelet $4.50 is no bargain, but the daily specials of sauced fish filets and seasonal seafoods at $4.25 to $4.50 are a good buy. Appetizers average $2, main courses $4.50, desserts $1.50. A glass of wine - a commendable Soave, for instance - costs only eighty cents. A carafe is $4.50. There are few wines, such as Mouton-Cadet and Muscadet, for $7 or $8, plus ciders, beers and a full bar. While you might spend $5 for a salade nicoise and a beer, a full meal with wine plus tip escalates to $10 or $12. Not bad in the middle of Georgetown, if you go when it is not crowded, pick a waiter who is smiling, and order one of the day's specials, something French that nobody would recongnize on the Eastern Shore.