For me, it began with THE POSEIDON ADVENTURE (John Williams). The main title is all about the ship itself, a mighty leviathan working hard to claw its way through the sea. The ship is a character. The body of the score is atmospheric, addressing the people as well as the setting. The end title starts off being about the people, and then gradually becomes an elegy to the ship, enormous and powerful. It was a formative experience and I never got over it.
After that, any movie about a big ship would seem interesting before I knew anything else about it. THE LAST VOYAGE, GOLIATH AWAITS, BEYOND THE POSEIDON ADVENTURE... the music didn't always make an impression, but I always had to watch the big ship movies when they came on. They were important.
When my family got cable, S.O.S. TITANIC (Howard Blake, 1979) was on HBO and Cinemax. I watched it over and over, and never tired of it. Blake scored the tragedy more than the ship itself, and did a great job. It kills me that a shortened and chopped-up version of this film is all we have on DVD.
I can't fail to mention RAISE THE TITANIC (Barry) and TITANIC (Horner). These are gold-standard scores, basic to our ecosystem, and need no introduction around here. Horner gets the most play from me, of all of them.
There's also "Dangerous Crossing" with Michael Rennie (1953), about a murder on an ocean liner. Intrada released the score a while back, by Alfred Newman and Sol Kaplan. It features re-recorded adaptations of music from The Snake Pit and The House on Telegraph Hill. The film used the same sets as the Clifton Webb/Barbara Stanwyck Titanic film.
One of my favorite unreleased, totally obscure gems, from the great John Addison. The opening titles definitely are a nod to The Love Boat, since this miniseries was also an Aaron Spelling production, and ran while The Love Boat was in its third season. It's basically The Love Boat meets Die Hard.