It's really not. The type of swinging work shanties that we think of as "pirate" or "nautical" music is present in a couple of folk bands - I'm thinking of Finntroll's more bouncy songs specifically - but there's not really anything like that in Epica's music.
If we're talking pirate metal, here's Alestorm (and I can't believe no-one in this thread, myself included, thought to mention them). There's a few other similar bands, but this here's probably the best.