Wahoo, tautog, arctic char: They sound more like creatures from the deep than tantalizing dinner choices. But the exotic fish dished out at Hook, Georgetown’s chic new temple of seafood, are anything but scary.

Hook’s vision comes from chef Barton Seaver, 28, best known for creating the U Street favorite Saint-Ex. The tongue-twisting fish on his menu come from stocks that help to preserve the world’s endangered marine populations, a practice called sustainable seafood that is catching on at Wal-Mart, Whole Foods and other chains.

“My power as a chef is to change minds through taste,” Seaver said. “If you don’t care about sustainable seafood … you’re still coming here and making a difference.”

Seaver’s commitment to sustainability, which began during his training at the renowned Culinary Institute of America, makes dining at Hook a worthy education in itself. Great restaurants first must appeal to the eyes and palate, however, and
Hook seduces one’s senses in stellar fashion.

The bar area is swathed in gray and translucence, studded with clever if clunky ship-captain’s swivel chairs and Italian light fixtures straight from a pop-art show. Jonathan Umbel, Seaver’s partner in the Pure Hospitality group that brought Hook to M Street, designed a layout that allows singles to mingle on the bustling ground floor and families to decamp to a quieter area upstairs.

Begin by trying the crudo, elegant knots of raw fish. While similar in concept to sashimi, Seaver’s crudo has more Italian influence and arrives with a dollop of dressing that teases out the fish’s hidden personality. Most tables try three crudo on one plate, which allows you to take a bite of each.

The waiter will invite you try a glass of prosecco, Italy’s fun-loving answer to Champagne, with your crudo plate. The pairing is pleasing, but the price goes unmentioned: $9 a glass, which can add up for a table of impulsive fish lovers.

Try splitting a bottle of wine instead. Seaver, a certified sommelier, has chosen vino of all varieties and costs, and the easygoing servers don’t mind if you try a taste first. Mixed drinks also are prepared at the bar with fresh juices.

Wahoo, delicate and white-fleshed when cooked, leaves a trace of creamy olive on the tongue when nibbled raw with a sliver of orange and basil leaf. Yellowfin and blackfin tuna, both served with mint and lime salt, can be compared side-by-side in an irresistible taste test. (The blackfin is beefier, but both are worthy.)

The most impressive crudo is trout roe, tinted a blazing coral and topped by a pearl of crème fraiche with one tiny, buttery brioche cracker to finish. Trout roe are saltier and less fragile than the eye-shaped salmon eggs common in Japanese restaurants. Layer everything on the cracker for the optimal experience.

For a second course, Seaver and chef de cuisine Joshua Whigham, a veteran of Spaniard Jose Andres’s high-flying kitchen, serve up several splendid salads. None will disappoint, from the easygoing local greens blend, swirled with pine nuts and sweet onions, to the bolder Caesar salad with sharp stravecchio cheese and salty Spanish boquerones fish.

Yet two non-traditional salads may tempt you most. Grilled calamari, which many otherwise great restaurants overcook into a rubbery mess, comes out fabulously woody with a basil-walnut pesto and warm potato salad so addictive that I had to resist asking for seconds. The beet salad, woven with leafy greens and blue cheese, excites then calms the palate.

These manifold joys of the menu are outdone by the entrées, a rotating cast of esoteric cuts obtained sustainably each week.
You might not see tautog on your first trip, but the weakfish, also called the gray trout, is an equally rare alternative with a splendidly nutty tang enhanced by almond picatta sauce. Saffron risotto and shredded arugula add bitter and spicy notes to the mix.

Other fish are best explored through common bonds with fish you know and love. The pink and flaky cousin of salmon, arctic char arrives atop a forest-colored pyramid of Catalan spinach with crunchy curls made of the nutty sunchoke root.
Blackfin tuna, more akin to swordfish than its yellowfin brother when cooked, sails in on a pillow of potato puree so creamy and buttery that no human hand could have blended it so well. Red onion and fennel salad finishes the dish.

Sunburst trout dresses in smoky perfection suitable for steak with mushroom ragout, bacon and onions. The mahi-mahi, a more widely seen species that Seaver procures from select renewable populations, was the only entrée that failed to leave me breathless. Smothered by too-sugary sweet-potato mash, the mahi loses its starring role on the plate.

The dessert lineup at Hook, from the hand of former Citronelle pastry chef Heather Chittum, has too many highlights to come second to the entrées. The chocolate tart, dark and decadent, adds a sweeter note with caramel ice cream and a salty one with roasted cashews marching on its crown. My companion was reminded of Ben & Jerry’s famously rich “Chubby Hubby” ice cream gone upscale — in all the right ways.

Chittum’s Nutella-filled donut holes, handmade in a side sauce of bitter chocolate, leave an explosion of textural pleasure on the tongue. Brown butter almond cake reads heavily but tastes ballet-perfect.

The most unique dessert is also the lightest, paper-thin flowers of pineapple carpaccio that complement the dark-roast house coffee. The fruit is joined by a handful of hazelnuts and a scoop of fresh basil ice cream, an astounding finale for an astounding meal.

What you’ll enjoy the most:

The unusual varieties of fish, from wreckfish to amberjack, that break away from the standard salmon, swordfish and snapper. Service is excellent.

What you may dislike:
Be careful of the street lamp outside the second floor window that leaves several unlucky diners squinting into their salad. The lack of specialty cocktails is also disappointing.

If you like ________, you’ll love Hook:
Hook takes Oceanaire’s fresh-fish fixation to a higher and hipper level.

Don’t be turned off by:
Hook’s “sustainable seafood” angle. If you crave more information on recipes and the future of fish, it’s available. If you can’t stand fish altogether (but your date loves it), try the steak.

Typical guest:
Any of the capital’s stylish political daughters would be at home here: Cate Edwards, Alexandra Kerry or the Bush twins — whom the Washington Post spotted sharing the country ham a few weeks ago.

3241 M St. NW, 202-625-4488. Open Tue. and Sun. 5-10 p.m., Wed.-Thu. 5-11 p.m., Fri.-Sat.
5 p.m.-midnight; Brunch Sat.-Sun. 10 a.m.-2:30 p.m. Closed Mon. Appetizers $3-$11, entrées $22-28.