Aliza Cohen, left, and Khue Nguyen are dressed for the occasion on the Boomerang Pirate Ship. (Craig Hudson/For The Washington Post)

The newest party-cruise vessel on the Potomac River is a 54-foot, custom-built pirate ship outfitted with 12 water cannons, Jolly Rogers that flap in the breeze and a crow’s nest atop the mast. There’s also a full bar, a DJ booth and two levels of deck with enough room for 90 people and a cutthroat limbo contest.

Because it’s a pirate ship, the crew peppers their speech with “yaaaars” and refers to you as “matey.” You will be offered “grog” and tequila-heavy “Pirate Punch” at the bar, and be threatened with walking the plank if you don’t want to limbo.

So, this isn’t for everyone. There are those who would consider a two-hour pirate-themed cruise a violation of the Geneva Conventions. But there are plenty of others for whom an excursion aboard the Boomerang Pirate Ship presents an excuse for a goofy night out.

This is the sister ship of the Boomerang Party Yacht, a more conventional party boat that launched last year. The original’s indoor dance floor seems like a place to celebrate a bar mitzvah or prom. The Pirate Ship, on the other hand, looks like something from Disneyland, designed to excite kids and awaken childhood dreams in adults.

Co-owner Nikki DuBois says she and her husband, Dave, had family adventures in mind when they commissioned the custom-built pirate ship earlier this year. The boat takes children on a theatrical adventure Wednesday through Sunday, complete with a water cannon battle. But the couple also had a feeling that there were enough adult wannabe pirates out there to make it worth their while to host nightly cruises on the Potomac with booze, music and great views of the monuments.

Lisa Torzewski and Alyssa Barnett enjoy the music aboard the Boomerang Pirate Ship. (Craig Hudson/FOR THE WASHINGTON POST)

Some really get into the spirit. DuBois guesses that at least one-third of the adults who make their way onboard are decked out in some form of pirate garb, from women wearing off-the-shoulder blouses and black boots to guys in button-down shirts who tie on a skull-and-crossbones bandana. (An entire bachelorette party once showed up looking like extras from “Pirates of the Caribbean,” DuBois says.) Sadly, the night I sailed featured no pirate costumes outside of the crew, so DuBois wandered through the crowd passing out eyepatches and plastic cutlasses.

The trip itself is rather uneventful, departing from Georgetown’s Washington Harbour and cruising as far as Reagan National Airport or Old Town Alexandria before turning around and sailing back. The monuments and the Kennedy Center gleam off the water. There are two decks — the main deck and a smaller rooftop above the bar — where partiers can hang out. The upper level has benches where you can relax, while the more open main deck is good for dancing to the steady stream of contemporary pop hits and ’80s tunes. Thankfully, there are no sea chanteys, although reggae bands perform during some Sunday cruises.

Weather can put a damper on things. In case of rain, the ship sails for the Key or 14th Street bridges and idles underneath, waiting for precipitation to pass. (“Our pirate cove,” DuBois calls it.) In the case of more serious storms, the ship returns to the dock.

You may decide that the pirate life is not for you. But if you forget about being self-conscious for a couple of hours, have a few rum drinks and don an eyepatch, you may have a pretty good time, matey.

Boomerang Pirate Ship

Washington Harbour, 3100 K St. NW. 202-695-6597.

Ships depart at 7:30 p.m. Wednesday-Thursday; at 5:30, 7:30 and 9:30 p.m. Friday; at 4:30, 6:30 and 8:30 p.m. Saturday; and 2:30 and 4:30 p.m. Sunday. Each cruise lasts about two hours. Tickets cost between $20 and $30, depending on the time and day of the cruise.

Some passengers talk and drink, while others simply watch the city skyline as the Boomerang Pirate Ship sails down the Potomac River. (Craig Hudson/FOR THE WASHINGTON POST)