IF YOU'VE been house hunting, you know that sellers sometimes take artistic license with descriptions of their property. "Metro accessible" means there's a bus stop nearby -- maybe a few blocks away. The "back yard" is a patch of dirt the size of a postage stamp. And so on.

Nightlife has its own share of little white lies. A "happy hour taco bar" turns out to be a few stale shells and dry meat in a chafing dish. E-mails trumpeting "the hottest new club" don't mention that it's just a rebranded event at the same been-there, done-that location. And while some "Waterfront" spots are near the Potomac, you'd have to climb over fences or crowd-control ropes before getting close to the river.

There's nothing misleading about Cantina Marina (600 Water St. SW; 202-554-8396), a two-story restaurant and bar at the Southwest waterfront's Gangplank Marina. Snugly tucked onto a pier between huge dinner-cruise ships and the presidential yacht Sequoia, Cantina Marina is not just on the water, but over it.

An octagonal tower, which looks like a rather stumpy lighthouse, holds a tiny dining room and a handful of barstools, but what draws me back is the large split-level patio, with views of Hains Point and its golf course, planes taking off from Reagan National Airport and, from certain seats, the Washington Monument looming over long rows of boats docked on the Washington Channel. Refreshing breezes abound. With a margarita or rum cocktail in hand, it's easy to imagine you're escaping the Washington buzz for a place where shorts and flip-flops are the dress code.

Unlike some of its neighbors in this redeveloping neighborhood -- H2O, the Mandarin Oriental hotel, Zanzibar on the Waterfront -- Cantina Marina is not fancy. Under a tentlike canopy, a few dozen stools, high pub tables and two couches surround the long, rectangular bar. The menu lists twice as many beers in cans as bottles, including Pabst Blue Ribbon and the Mexican import Tecate, for $3 or $4 each. No matter what you order -- PBR, a nice Spanish wine, decent margaritas -- it arrives in a plastic cup that seems more suited for a college party. And hey, you can even dock your boat outside (call for details).

Young professionals flocking here for the lively happy hour join tourists and cocktail-attired crowds waiting to board the Odyssey and Spirit of Washington, or diners who'd rather enjoy Cantina Marina's excellent oyster po' boys or peel-and-eat Cajun-dusted shrimp at outdoor tables. "Eclectic" also describes the soundtrack, which throws up head-scratching medleys that include college rockers Fine Young Cannibals, punk icons the Ramones and smooth-jazz favorite Sade. (No, that's not hypothetical.) Live music, usually singer-songwriters or duos with guitars, is featured without a cover charge Thursday through Sunday, weather permitting.

Actually, much of Cantina Marina's traffic is dependent on the sun. Lacking walls, the canopy offers little protection from rain, and most seating is exposed to the elements, so when the forecast is gloomy, a trip to the waterfront loses some of its luster. I don't blame the staff for being overly cautious, but last Sunday, the patio was shuttered because of showers that never arrived.

Service can be laid-back. My friends and I recently spent a slow afternoon laughing and joking with the staff, who were tossing bread and crumbled nachos off the edge of the deck in an effort to lure some huge catfish to the surface.

Owned by Nick Fontana, who runs the popular Capital Q BBQ in Chinatown, Cantina Marina is an excellent place to kill a lazy summer day with friends, sipping cold drinks and taking in some great views. Some advice: Parking at the marina is extremely limited, so you may want to consider the 10-minute walk from the Waterfront-SEU Metro station. And that's the truth.

Cantina Marina sits on a pier on the waterfront in Southwest Washington. Unlike its upscale neighbors, such as H2O and Zanzibar, the bar is refreshingly laid-back, with a tent-covered patio and affordable prices.