With its tightly packed buildings and intensive network of tunnels and bridges, Manhattan hardly seems isolated. But it is an island, nonetheless, with a 32-mile coastline. Small wonder that some of its greatest adventures lie on the water.

The Trip’s the Thing

Almost every local cruise operator focuses on New York Harbor, mixing spectacular sights, slightly salty air and the thrill of water travel into a magical cocktail. In guided 60- or 90-minute tours, the enclosed vessels of CitySightseeing Cruises New York (Pier 78, 455 12th Ave, at W. 38th St., 212.445.7599) glide past the iconic Statue of Liberty, Ellis Island and a trio of bridges—the Brooklyn, the Manhattan and the Williamsburg; the longer voyages also take in Midtown landmarks, from the Art Deco Empire State Building to the gleaming United Nations perched on the edge of the East River. The most memorable vistas occur during early-evening departures, when the cityscape is framed by the setting sun.

Fine dining is integral to a cruise on World Yacht (Pier 81, W. 41st St., at 12th Ave., 212.630.8100), which dispatches a flotilla of enclosed, white-tablecloth restaurants down the Hudson River to Lady Liberty and back, delighting patrons with skyline settings and surf ’n’ turf classics (pan-roasted duck, marinated skirt steak, grilled mahi mahi) prepared on board. Hornblower Cruises (Hornblower Landing, Pier 40, 353 West St., 212.337.0001) also offers elegant, four-course meals, plying Gotham’s blue brine in green fashion: The Hornblower Hybrid, the newest member of its four-ship fleet, is powered by solar panels and wind turbines, providing eco-conscious visitors with a low-impact loop around lower Manhattan.

Freshly remodeled, the luxury yacht Zephyr (Pier 16, South Street Seaport, 866.985.2542) boasts plush upholstered booths in its closed, climate-controlled decks, as well as an open top deck. Full-service bars trimmed in mahogany allow patrons to drink in potables as well as behind-the-scenes sights on its Hidden Harbor Tours. On the Brooklyn Tour (Jul. 10), for example, the Zephyr heads along the East River past the historic Brooklyn Navy Yard—recently turned to civilian use after more than 150 years of military duty—the new Brooklyn Bridge Park and commercial terminals.

Despite such extensive development, New York Harbor remains a major avian flyway. Teaming up with Audubon Society experts, New York Water Taxi (Pier 17, South Street Seaport, 866.989.2542) offers the birds’ perspective, if not a bird’s-eye view, on its weekly NYC Audubon EcoCruises, which traverse Jamaica Bay and small islands that house various waterfowl. The residents aren’t disturbed, thanks to the vessels’ low-wake hulls and hospital-grade mufflers.

Going Places

As its name suggests, New York Water Taxi also furnishes transport, with a Hop On/Hop Off service that stops at various docks (including Christopher St., Battery Park and DUMBO, Brooklyn), allowing passengers to explore neighborhoods and sights. The Battery Park stop, for example, is within walking distance of the National September 11 Memorial (request a free pass when buying the NYWT ticket).

In fact, some of the city’s most enduring attractions can only be reached by boat—notably the Ellis Island Immigration Museum, onetime arrival point for millions of immigrants, and the Statue of Liberty, their one-woman welcome committee. Statue Cruises (17 State St., 201.604.2800) heads to both (doable in one day, if you set out in the morning). The free ferry to Governors Island departs from the Battery Maritime Building terminal (10 South St.), an Easter egg-colored, Beaux Arts confection of cast and wrought iron; it’s a fast ride back in time to the green isle, dotted with red-brick buildings, ruins of forts and contemporary art installations, that seems to rise out of the water to greet you.

An even more exotic place, by New Yorkers’ standards, is the Garden State. The SeaStreak Ferry catamaran (Pier 11, at Wall & South sts., or E. 35th St., at the East River, 800.262.8743) offers an easy, hourlong commute, complete with sundeck and a glorious harbor view, to Gateway National Park in Sandy Hook, N.J.—a haven for swimmers, hikers and birdwatchers.

Nautical Thrills

Sometimes, the ride itself is the attraction. Sporting a painted toothy grin on its bow, the Shark Speedboat Thrill Ride (Pier 16, South Street Seaport, 866.985.2542) tears around the tip of lower Manhattan for 30 minutes, churning up excitement and spray as it passes the Financial District before zipping back to the pier. The Beast, a neon-green, red-jawed vessel operated by Circle Line Sightseeing Cruises (Pier 83, W. 42nd St., at the Hudson River, 212.563.3200), charges south from Midtown at 45 miles an hour, pausing only for a photo op with the ever-obliging Lady Liberty.

Slow-moving traditionalists may prefer to see her the old-fashioned way, from seats on the Pioneer (Pier 16, South Street Seaport, 866.985.2542), a restored double-masted 19th-century schooner that sails out of South Street Seaport, under the Brooklyn Bridge and around the harbor. An even more retro boating experience is available at the Central Park Lake Loeb Boathouse (E. 72nd St., at Park Dr. No., 212.517.2233). An authentic Venetian gondola, complete with gondolier, can be rented for parties of six; rumor has it that the oarsman can be persuaded to sing.

Staying in Port

Finally, there are vessels that transport people by going nowhere, amid crying seagulls and the slap of waves. Case in point: the Intrepid Sea, Air & Space Museum (Pier 86, 12th Ave., at W. 46th St., 212.245.0072), a repurposed World War II aircraft carrier moored on the Hudson. Vintage military flying machines are preserved on deck; the latest exhibit, opening Jul. 19, is the Enterprise, the never-flown space shuttle prototype. Before being decommissioned, the Lightship Frying Pan (Pier 66 Maritime, 12th Ave., at W. 26th St., 212.989.6363) illuminated the dangerous shoals off Cape Fear, N.C.; now, docked alongside Hudson River Park, it reopens every summer as a shabby-chic bar and grill with much of its original décor intact. Summertime lounge The Crow’s Nest, situated on a stationary barge atop restaurant The Water Club (East River, btw E. 28th & E. 32nd sts., 212.683.3333), aims for a loftier vibe, serving oysters and seasonally appropriate cocktails, such as bourbon iced tea and vodka-spiked lemonade. Bargemusic (Fulton Ferry Landing, Brooklyn, 718.624.2083), a coffee barge transformed into a cozy concert hall under the Brooklyn Bridge, anchors fans of chamber music; this month’s lineup includes noted pianist Ursula Oppens (Jul. 7-8) and the Flux Quartet, a modern-oriented string ensemble (Jul. 6, 11 & 18).

In short, it’s easy to cruise around town, sail to not-so-distant shores or visit floating destinations. Bon voyage!