Where Up Is Down, and Down Is Up : At San Pedro’s West Channel Bar & Grill, fun food is on the top floor; for serious dining, go down a flight

Here we go up the big staircase, angular neon structures hanging over our heads like radiant riddles. At the top we find a long, bright room crowded with tables where young people are shouting to each other over a rock ‘n’ roll sound track. It’s a world of noise and animation with a pleasantly distracting view of San Pedro’s new Cabrillo Marina.

Here we go down the staircase again, and it becomes obvious that at West Channel Bar & Grill, the bar and grill part is upstairs. Downstairs is definitely a restaurant, and a rather cozy, sedate one with muted lighting and a piano stylist playing “Daniel” and “Misty.” The seats farther from the windows are elevated, but not to much purpose; down here the marina view is discreet rather than distracting.

Not that the decor isn’t fashionable downstairs. Tiny Diva lamps illuminate tasty abstract paintings with an ironic early-’60s feel to them, and it goes without saying that the air ducts are exposed. Unlike most exposed air ducts, however, which look as if they’ve been exposed merely to humiliate them, these are actually good-looking. Gleaming and metallic with sharp, clean lines, they’re positively exhibitionistic.

Back upstairs. The bar and grill room is called the Bistro, but it’s not like any bistro you’d see in France. The wall-long bar goes through several changes over its length, from rotisserie to oyster bar to sushi bar to just plain bar. Not much is served here but snacks: mostly sushi bar stuff, dim sum, salads and sandwiches. On the other hand, snacks are about all these tiny tables will hold.

Sometimes they can be a snack on the wild side--a venison French dip sandwich has been listed--but mostly they’re more upscale nibbles. The half-pound burger is made with very freshly ground meat; you’d gladly eat it without so much as mustard on it, and West Channel knows this. The only condiments automatically supplied are a bowl of onions, tomatoes and gherkins.

There are also some substantial entrees up here in rock ‘n’ roll heaven, rotisserie stuff and pastas, mostly. One is also served downstairs (though as an appetizer) a very successful dish of duck sausage with blue corn polenta, topped with sun-dried tomato strips and fried shreds of leek. Possibly the best thing available up here is the dreamily light-textured Chinese chicken salad, one of the best chicken salads anywhere.

For serious eating, though, we have to go back downstairs. Chef Katsuo Nagasawa is a veteran of La Petite Chaya, Max au Triangle and the Irvine edition of Bistango, and a couple of dishes clearly reflect this history. For instance, the heavy but satisfying cucumber and gravlax parfait--layers of julienned cucumber and salmon dressed with olive oil, sour cream and salmon eggs--dates from Bistango.

Much of the time Nagasawa is putting his own personal spin on classic dishes. His oysters Rockefeller do not emphasize the spinach topping and there is no detectable anise flavor. Mostly they taste of a wonderful cream sauce flecked with red pepper. His Louisiana crab cakes, which are thick and have a respectably good texture, come in a buttery sauce with an oddball but not insane garnish of grapefruit sections and a “deep-fried vegetable spaghetti” which seems to be more browned shreds of leek.

The best of the appetizers is a gratin of mixed mushrooms: shiitake , oyster, chanterelle and probably some enoki . It’s rich and delicious in a wine and cream sauce, and there’s a sly bit of cheese underneath the mushrooms. Pay attention to the simple green salad, too--a big plate of half a dozen salad greens is $2.50, the price of an iceberg lettuce salad anywhere else.

Sometimes, things do get out of hand. Octopus and sweetbreads make an appetizer that is almost as bizarre as it sounds: one gentle sweetbread and a scary-looking section of chewy red octopus tentacle, served sucker-side up, all in pesto sauce. Nagasawa is really begging our indulgence on this one. And the seaweed salad in ginger French dressing is heavily depth-charged with seaweed. You seriously have to like seaweed to go for this one.

Half of the pastas are stuffed, and while West Channel seems proudest of the half-moon ravioli--filled with chicken-and-leek mousse in a bittersweet sun-dried tomato cream sauce--the others are at least as good. The mushroom- and spinach-stuffed giant ravioli come in a tangy light tomato cream sauce, and the multicultural gyoza , stuffed with shrimp and scallops, are awash in a rich, tart tomatillo butter.

When this kitchen is on top of its game, the results can be dazzling. The mignonnette of beef is a filet, grilled and sliced, served on a thin bed of mashed potatoes and topped with a toasty coating of bread crumbs mixed with garlic and tarragon. On top of this are jicama chips (neutral in flavor--the matzo of exotic vegetable chips), and around the base is a strong red wine reduction. Off in the corners of the plate are some ratatouille and a mound of couscous so strongly flavored with saffron you only want to sprinkle it here and there on other things.

That’s an adventure. Even grilled whitefish takes on glamour in an orange-ginger butter that tastes as though there’s a splash of balsamic vinegar in it. The fish rests on a bed of new potato, sliced paper-thin, and there are wild mushrooms on top of the whole thing.

Sometimes, Nagasawa skates unfortunately close to the edge. I can’t imagine what the four raspberries are doing on the plate of exquisite sand dabs scattered with julienned carrots and zucchini, and there’s a sweet mint-like flavor in the grilled lamb that seems determined to keep the meat from tasting of lamb. The vegetable timbale wrapped in thin sheets of eggplant and the fried potato patty that come with it certainly help out, though. A big veal chop comes with the same potato cake and an onion marmalade sauce that’s a hair too sweet.

The main problem with the food, though, is the service. Once when I ordered swordfish paillard--which should have been a thin grilled slice of swordfish with homemade potato chips--I got blackened swordfish with black beans and some cute tiny vegetables. It was pretty good, especially since it happened to be one of several dishes with the American Heart Assn. symbol, but it wasn’t what I ordered. And I’m still not sure why the chicken stuffed with foie gras that I got had a white stuffing flecked with green, tasting distinctly of goat cheese.

The desserts are good enough, though you wouldn’t come here for them alone. Well, maybe you would for the chocolate walnut tarte with caramel sauce. The very creamy creme caramel is not cluttered up with blueberries or anything, and doesn’t need the sugar crust that’s obviously added at the last moment (cold custard, hot crust). There’s a minimalist apple tart with slices of apple you could read a newspaper through, and a solid cheesecake with a good grainy texture. But that’s it for dessert.

And that’s it for the serious eating. It’s time go back upstairs and shout at each other over the tiny tables.

West Channel Bar & Grill

285 Whaler’s Walk, Cabrillo Marina, San Pedro; (213) 831-5090.

Open for lunch downstairs, 11:30 a.m. to 2 p.m. Monday-Friday and upstairs 11:30 a.m.-3 p.m. daily; dinner 5-10 p.m. daily. Full bar. Parking lot. All major credit cards. Dinner for two, food only, $30-$60.

Recommended dishes: Louisiana crab cakes, $7; gratin of mushrooms, $6.75; duck sausage with blue corn polenta, $6.50; giant ravioli, $7.50; mignonnette of beef, $16.50; whitefish, $14.50; chocolate walnut tarte, $4.