Echoes by Pink Floyd
Burning Sensations - Belly of the Whale
Styx - Come Sail Away
Christopher Cross - Sailing
Sea of Madness by Crosby, Stills, Nash, and Young
Ocean Size by Jane’s Addiction
Ebb Tide
Slow Boat to China
Little Boat (O Barquinho)
Victory at Sea (probably not right for your party)
Red Sails in the Sunset
I Cover the Waterfront
Harbor Lights
Shrimp Boats is a-comin’
You have to include *Under the Boardwalk * by the Drifters.
Also if you can find it, “Three Little Fishes” (Fishies?) by ?
The one with the “doot, doot, diddum, daddum, waddum, chu” refrain.
You know which one I’m talking about.
Here’s a great party tune, though it’s an oldie:
"Come On Down (To My Boat) by Every Mother’s Son
“Dirty Water” by the Standells
both will do well in the “makeout room”
Women and Men and Cow Town by They Might Be Giants. The first is essentially a sea shanty, and the second is a hybrid sea shanty/cowboy song.
And there’s the entire score of “Pirates of Penzance”
Anything by Billy Ocean, The Ocean Blue, The Waterboys, British Sea Power, or Great Big Sea 
Underwater Moonlight, by the Soft Boys
Underwater Love, by Smoke City
This Is the Sea, by the Waterboys
Brides of Neptune, by Cracker
Velvet Sea by Phish
All at Sea by Jamie Cullum
River, Sea, Ocean by Badly Drawn Boy
Lost Sailor - The Grateful Dead
The Wild Wild Sea - Sting
‘Dock of the Bay’ by Otis Redding
Pretty much the whole catalog of The Beach Boys and a ton of stuff by Jimmy Buffett.
I think there are a few Pixies songs that’ll do the trick.
Where Is My Mind?
Mostly for the second verse
Wave of Mutilation
Thing That Should Not Be by Metallica It’s a lovely song about Cthulhu and kindred horrors.
Plus H.M.S. Pinafore, Peter Grimes, Billy Budd, The Flying Dutchman, Victory at Sea, etc.
Will there be geeks there? If so, include
NaCl (The Salt Song) by the McGarrigles, about the irresistable attraction between “just a little atom of chlorine, valence minus one” and “handsome sodium, with enough electrons on his outside shell, plus that extra one”.
Somewhere in the deep blue sea there’s a negative
For my extra energy, yes, somewhere in this foam
my positive will find a home
Then unsuspecting chlorine felt a magnetic pull
She looked down and her outside shell was full
Sodium cried “What a gas, be my bride!
And I’ll change your name, chlorine to chloride”
The Mermaid Song - Brobdingnagian Bards
The Killing of the Whale - Henry and Sid Kipper
Albums by Stan Rogers
I particularly like: Three Fishers
Tiny Fish for Japan
Lock Keeper
While Cruising Around Yarmouth - A. L. Weber - He sings much about Sea faring.
The Down Towner Motel - Lee Murdock And Kevin ODonald
Saint Grendins Fair Isle -
The Homebug Steamship Co - Debbie McClatchie About the steamships taken to California during the gold rush.
Ghosts of Cape Horn - Gordon Lightfoot
Christian Island (Georgian Bay) - Gordon Lightfoot
Wreck of the Edmund Fitzgerald - Gordon Lightfoot
May I suggest:
–“A Salty Dog” by Procol Harum
–“The Ocean” by either the Velvet Underground (original version) or Lou Reed (revised version)
–“Sea Cruise”