When you think of musical cruises, you likely don’t imagine Speedy Ortiz at the ship’s helm, guitars in hand, blasting indie rock into the waves of the Charles. Head to Seaport Boulevard on Sunday afternoon, though, and you can catch a glimpse of them breezing by doing just that.

Following in the footsteps of bands like Widowspeak, Paramore, and Weezer, Speedy Ortiz are gearing up to play live on a cruise ship. Their performance Sunday afternoon is a part of Rock and Blues Cruise Concert Series that sets sail from the World Trade Center Pier in the Seaport District and proceeds to travel for three hours around Boston’s scenic waters, an event partly organized by Bowery Boston. “I feel like they thought it would be funny if we played on a boat, honestly,” laughs Dupuis. “Most of the other bands that do this aren’t indie rock bands, so we want to figure out how to make this even more funny.” They’re shaking things up in the best way: nonconventional openers.

Speedy Ortiz is usually pretty stringent with who they want to play with, so they were specific in who they chose this time around. The most absurd of the crew is Rhode Island punks Downtown Boys, a choice frontwoman Sadie Dupuis handpicked immediately. “It’s going to be awesome to hear anti-capitalist punk music on a fucking cruise ship,” she laughs, still in disbelief that they’re actually on the bill. “We’re a band that grew up playing and still plays basements, which makes it funny to imagine us singing on a boat while drinking cocktails with little umbrellas in them. Our roots are in DIY, basement shows, and punk, so as out of the ordinary as this boat show is for us, Downtown Boys will keep us in our element.”

Then there’s Francine. The five-piece Boston band hasn’t released new music for almost a decade and barely plays shows (though you may have caught them at one of the final T.T. the Bear’s Place shows), but the underrated act write licks too original to be buried over time. They failed to get much critical acclaim outside of the city during their prime years in the early 2000s, but Dupuis is hoping to shine a light on them once again. “In terms of songwriting, they’re the band I rip off most often,” she admits. “Their songwriting is distinct and there’s all these little tricks that I consider key elements of their songs that I slip into Speedy songs.”

Dupuis first came across Francine when a beloved local high school band that bassist Darl Ferm went to school with brought the main singer onboard to produce their album. Then, while studying at MIT, Dupuis ran into them again when they covered “Off You” for a Kim Deal cover compilation. “I’m an obsessive fan of this band, but I know maybe five people who are as obsessed with the songwriting as I am,” she says. “My old bandmate and I opened for them at T.T.’s several years ago just from emailing them obsessively asking to play. We may have scared him because we didn’t talk much, but I’m so excited to get to play with them again. Clearly I’m a huge, nerdy fan. I sent a request list of maybe two dozen songs I want them to play. Hopefully I’m not too embarrassed to talk to them.”

To shake off some of the nerves, we threw the most essential boat-related questions her way to prep for the trip. So dawn your sunglasses, raise your piña colada, and toast to the ship that will (soon) set sail while we roll through rapid-fire questions on yacht rock,  cannonballs, and beyond:

Are you a cruise regular?

I’ve never been on a cruise. We played on a boat once in France which was sort of weird and fun, but it wasn’t a cruise boat or ever set sail. We’ve played on the Hudson River before for a festival the Village Voice sponsors. They docked a boat next door for VIP, but I never stepped on it. I’m not selling this show well. I love boats! This is going to be the best! I love boat cruises! I just haven’t been on one before [laughs].

What’s your favorite drink for lounging by the pool?

Oh my goodness. I like simple things, so I want a coconut cut off at the top. Sippin’ out of a coconut. You know what’s funny? You know that David Foster Wallace essay “A Supposedly Fun Thing I’ll Never Do Again” where he hates being on a cruise? I definitely taught that to my class when I used to teach at UMass.

Would you do an impromptu reading of it?

I have the book, so I can definitely bring it along. I did almost try to go on the 311 cruise this year. I think it’s in Jamaica. I didn’t know any of the other bands playing other than 311. I just thought it was funny. There’s not going to be a 311 cruise in 2016 either, so I guess I’m SOL.

SPF or tanning oil?

I’m a stay-inside-until-it’s-dark-out person. I suppose I would choose SPF if I were forced to be in the sun.

What’re your thoughts on yacht rock?

Who qualifies, like Steely Dan?

Yeah. It’s pretty loose though in bands: The Doobie Brothers, Michael McDonald, Stevie Nicks…

I guess I don’t know a ton about yacht rock in general other than I assume Steely Dan qualifies. I know pretty little about yachts, too. Michael McDonald is considered yacht rock. Hall & Oats – I’m named after one of their songs so I guess I love yacht rock.

Dream cruise location?

Alaska. That’s a real cruise that they do! I’m not sure where it would begin. Probably on the west coast. Alaska is one of the few states I haven’t been to, so that’d be cool.

What’s the most underrated pool toy?

Did you see that video of all the bears in the pool? A family of bears do some Goldilocks shit. They get into the backyard of some suburban New Jersey family and climb into their tiny pool and play with their panning floats. They’re tossing the floats back and forth! I guess pool floats, as a toy, which are not conventionally used that way. Those bears seemed to be having a pretty good time.

If you could swim with any sea creature, what would it be?

I really like otters. I think they’re super cute. That’s not really going for the gold, but I think they’re quite cute, like little doggies.

You know how they hold hands?

They hold hands with each other?!

Yeah! Sea otters hold hands while they sleep so they don’t drift away.

This is so cute. Oh God. They’re just so cute. I wanna hang with them and maybe become them. There’s a valentine that says ‘You’re my significant otter.’ They sleep on their backs in the water, too! I could learn a thing or two from the otter.

What’s your go-to diving board move?

I’m terrible at diving. I had to quit swim team when I was in middle school because I can’t dive. I guess I’d cannonball. It would probably turn out more like a bellyflop because I am uncoordinated.

What’s your favorite boat-related music video?

Do you know that Liars video for “Scissor” where he wakes up on the boat and everybody’s dead and rocks keep falling from the sky? It’s really scary.

I hope you’re not picturing that for the cruise.

Seriously [laughs]. It’s between that and Aaliyah’s video for “Rock the Boat”. A lot of dark boat thoughts.

SPEEDY ORTIZ W/ DOWNTOWN BOYS, FRANCINE, AND DJ MICHAEL V. WORLD TRADE CENTER PIER, 200 SEAPORT BLVD., BOSTON. 12PM/21+/$25. ROCKANDBLUESCRUISE.COM.