Joey: Don't say I never gave you nothing.
Trillian St. James: What the hell are these things?
Finnegan: Real unfriendly.
Finnegan: Like a fine wine, I'm aging gracefully, thank you.
Mason: Like a fine wine my ass. You look more like a keg of beer to me.
Answer: According to some good old Google Fu, a single torpedo hit could absolutely destroy and sink a cruise ship since they're not as fortified as a warship would be. They're meant to carry passengers, not go to war. Granted, it probably wouldn't be quite as dramatic an explosion, but you could also argue that any other explosives on Finnegan's ship, plus the cruise ship's fuel, could have been ignited in the blast. You also have to factor in that the ship was already heavily damaged from the monsters attacking and was in a more fragile state than it would otherwise be.
TedStixon