The gritty summer rush hour of the Southwest Freeway is hardly heard a few blocks away at the edge of the Potomac. Sunbathers fold up their towels, a man in a three-piece suit heads with his briefcase down dock 'G' and shoppers in shorts return with grocery bags. At Gangplank Marina, it's time to start dinner.

In a neighborhood where a two-foot leap might carry you from one doorstep to another, where boat names are sooner remembered then last names, groups gather daily for drinks and talk. Neighbors know more about each other's garbage than jobs. In this close-knit community the common problem is space.

Nowhere more acutely than in the kitchen -- or galley. Clever menu planning might mean concocting a dinner that uses only one pot. Timing can be a problem; propane-powered ovens produce uneven temperatures, so it may take 30 minutes longer -- or shorter -- to bake a cake from one time to the next. And alcohol stoves on sailboats can be slow and inefficient.

Then there's the moisture factor. Transferring opened packages of crackers or cereal to sealed containers is a must. Otherwise a bag of peanut butter chips may melt into a single clump.

The stories from houseboaters go on: bending a pan to fit Thanksgiving Day turkey into the oven, computing the amount of water needed to wash the dishes in the winter when there's only tank water, storing frozen foods outside during chilly months. These compromises are the social cement in this floating city of about 130 doctors, lawyers, "river rats", divorcees, singles and families.

A waiter at Gary's restaurant and a performer at local dinner theaters, Robert Biedermann's galley looks like a stereotype of a single's kitchen: dirty dishes in the sink, an empty jar of Cranapple juice and a jug of wine left astray on the counter.

Tanned and barbacked (informality is the fashion at the marina), Biedermann likes to entertain. But with only a 3-inch-high broiler, he can't make rack of lamb or broil a steak. "And if I want to make something like gazpacho," he says, pointing to the blender on the small counter, "that whole counter becomes gazpacho. I can't be filleting fish at the same time." If he wants to have fruit salad, it has to be the main course, since there's no room for anything but the fruit in the refrigerator.

Some of Biedermann's adaptions: When he makes steak, he marinates the meat overnight to tenderize it and then cooks it on top of the stove. When poaching fish, he puts a plate on top of the pan instead of a cover and melts the butter on the plate instead of in another pan.

Unlike Biedermann, Eleanor Cruze doesn't take the time to cook. Her boat was destroyed by the marina fire this past November, and she spends free hours refurbishing her new boat. To avoid the heat in the cabin, sometimes Gruze sets up her electric skillet on dock and cooks simple meats there (hibachis or barbecues are strictly prohibited at the marina). When cooking inside, her speciality is garbanzo bean soup, which not only fulfills the one-pot rule, but also lasts the whole week.

When the Rubright family moved from their home to a 37-foot sailboat, Sharon Rubright refused to leave her china and silver behind. The evidence is in a contraption worthy of James Bond: a dining table with a sliding hidden compartment.

That's not the only hidden compartment in the Rubrights' cabin. A slender cabinet near the hatch "is where Richard lives," says Sharon Rubright as she points to her son's crescent-shaped mattress inside.

Eight-year-old Becky's "room" is a berth crowded with dolls, among them, of course, a mermaid doll. On this evening, after a dinner of peanut butter sandwiches and cantaloupe chunks, the children chase each other around the sailboat and are scolded, not, in this case, for playing on a neighbor's lawn, but for running onto a neighbor's deck.

They usually help their dad make dinner, although there's only enough space for him in the galley. Becky's job is making the salads. She's also the emergency chef when a thunderstorm makes stove cooking difficult. Richard washes the deck and makes all the sauces. The enterprising 7-year-old is bolder than most boat dwellers at Gangplank, who don't fish in the Potomac. He recently caught a blue gill, cleaned it, added a little tobasco and seasoning and steamed it. "Becky's friends thought it was gross, they were screaming," boasts Richard.

Above the three-burner gimbeled stove are two wall cabinets, storage space for canned and dry goods. A stainless steel double sink is about the size of one normal sink, a small one. The Rubrights have no freezer so they shop two or three times a week. ("I don't have the problem of taking things out of the freezer," says Sharon Rubright. "They're already out of the freezer.")

Unlike the Rubrights, William and Marjorie Mayo weren't prepared to give up luxuries when they moved from their McLean home to a 44-foot trawler. Because, as Majorie Mayo says, "We don't like steaks on paper plates," they have a dishwasher on their boat, as well as another rarity, an ice maker.

When Marine Cuisine owners Sue Mercill and Liz Levy cater boat parties, they always bring along canned goods. If the power fails, they may have to completely change the menu. Or call the food something else. t

Once when they made salmon pate, the refrigerator ended up not working and the pate ended up not firming enough to hold its shape. It became salmon mousse. Later, Levy got an order from a client who had heard about her "wonderful salmon mousse."

Then there was the time they were doing a party for 200 and only one burner was working. The hors d'oeuvre was 35 pounds of Italian sausage. Although it took them four hours to cook, the merriment of the party held them in good stead and, according to Levy, nobody knew what had happened.

The two women, who live at the marina, provide food for small get-togethers, corporate yacht parties and even racing rations. Levy went into the business full time when her job at the EPA ended with the Reagan administration, and says she asked Mercill to join her because "she had a crab pot."

According to Levy, people eat a tremendous amount on the water. "They think they're hearty seamen," Levy said, "Some even think it's the salt water that makes them so hungry." The magic of the salt-free Potomac.

Levy and Mercill's boats are crowded with cooking paraphenalia. Levy's compact galley on her boat, "Misdemeanor," houses a microwave oven, a food processor, a can opener, a full-size Hotpoint refrigerator, rows of spices, and utensils in colorful plastic containers and a folding table that opens to seat eight. ("Eight boat people, or eight apartment people who are very good friends," says Mercill.) Because the sewing machine, Christmas tree and ornaments in her "basement" (storage area in the boat's bilge), Mercill keeps Marine Cuisine's trays and crab pot there, mushroom baskets under her bed and doilies under a booth in her galley. That's in addition to providing space for her two cats, a dog, a son and a husband.

Two hours before launching at a party for 19, Mercill was cleaning the seven pounds of shrimp that Levy would use for the scampi. Hopefully the scampi. Levy didn't know if the generator would be working once they left dock, so she steamed the shrimp before going out. If they were forced to serve it steamed with sauces, it would be ready; if the generator worked, she could then saute it for the scampi.

By the time the "Wild Rose" pulled away from dock, the buffet table was set with appetizers.

By the time the boat pulled in, there had only been one wake (waves caused by a passing boat), but luckily Levy (who ordinarily can't manage eyeliner when the tides change) had this time grabbed vulnerable pots. At dock, the galley looked like the messy remains of any onland dinner party. And the guests had eaten scampi. MARINE CUISINE SCAMPI (4 to 6 servings) 2 pounds large shrimp 1/4 to 1/2 cup butter 3 cloves garlic, minced Salt and pepper to taste 3 tablespoons lemon juice

Shell and devein shrimp. Melt butter in a large frying pan. Add garlic. Bring to a sizzle, being careful not to brown butter.Add shrimp and saute 8 to 10 minutes until shrimp lose their opaque color and turn white. Season with salt and pepper. Sprinkle with lemon juice before serving. ELEANOR CRUZES GARBANZO BEAN SOUP (10 servings) 4 smokey link sausages, thinly sliced Olive oil for frying 1 large onion, diced 2 1-pound cans chick peas, undrained 28-ounce can whole tomatoes, undrained 1 large potato, diced in small cubes 3 medium carrots, diced Salt and pepper 3 tablespoons fresh chopped parsley 2 to 3 teaspoons oregano 1 1/2 teaspoons basil 1 cup dry white wine

Heat olive oil in a pot and brown sausages. Remove with slotted spoon. In the same pot, saute the onion until soft. Add the remaining ingredients (remembering not to drain chick peas and tomatoes) and simmer, covered, approximately 1 to 1 1/2 hours, until the vegetables are soft. Serve with sourdough french bread. SUE MERCILL'S STUFFED MUSHROOMS (Makes 28 to 32) 28 to 32 medium to large fresh mushrooms 1 cup beef bouillon 1 1/2 tablespoons butter 1/2 cup grated onion 1/2 cup grated celery 1 tablespoon minced garlic 1 package frozen chopped spinach, thawed 1/8 teaspoon nutmeg 1 1/2 cups shredded swiss cheese 1 to 1 1/2 cups shredded wheat cracker crumbs

Wash and remove stems from mushrooms. Set aside.

Put beef bouillon in a skillet and bring to a boil. Place mushrooms in the skillet in a single layer, stem side up. Cover and steam until liquid forms in the center of the mushroom. Remove from pan.

Melt butter in the same skillet. Saute onion, celery and garlic until transparent. Add thawed spinach (do not squeeze dry) and nutmeg. Stir and heat thoroughly for 5 minutes. Remove from heat. In a large bowl, mix cheese and vegetables.

Add enough of the cracker crumbs until mixture becomes fairly stiff and can be shaped into a mound. Fill the mushrooms with this mixture, mounding generously. Sprinkle a pinch of cracker crumbs onto each mound. Place under broiler to heat through. ROBERT BIEDERMANN'S ADAPTED CHICKEN WINGS MARCEL (4 servings) 18 chicken wings 3 tablespoons olive oil 1/4 cup white or red wine Water to cover 1 small onion, quartered and stuck with 4 cloves 1 bay leaf 1/2 teaspoon dried thyme 6 peppercorns 3 large sprigs fresh parsley 1/2 teaspoon salt 4 tablespoons butter 2 large cloves garlic, peeled and finely minced 1 cup finely minced fresh parsley 1/2 pound spinach fettucine 1 pound mushroom caps, steamed

Cut off the bony tip of each wing and discard them. Saute the remaining larger wing pieces in olive oil and wine until they just begin to turn golden. Cover with water and add the onion, bay leaf, thyme, peppercorns, parsley sprigs and salt. Cover and cook on low heat for 30 minutes.

Drain the wings. Melt the butter in a large skillet. Add the wings and saute until golden brown, about 4 to 5 minutes, allowing the wings to crisp a little. If you like crispier wings, continue to sauteing for an additional 10 minutes. Add the garlic and minced parsley to the skillet. With a spatula, quickly toss and saute the wings with the parsley and garlic, about 2 minutes.

Cook the spinach fettucine and mound in the center of a platter. Arrange chicken wings and mushroom caps around it. Adapted from "The Best of Electric Crockery Cookery''