A cruise ship is the perfect place to get acquainted with new dishes, seafood and otherwise. You have the right idea; order something you are familiar with, and also try something new. If you don't like it, no harm done--no extra charge.
I have discovered many new delights that I would not order in a restaurant for fear of not liking it and wasting money. In most cases, the seafood is frozen, not fresh, so it will not be the absolute perfection that some seafood aficionados require, but most people find it quite acceptable.
So live it up! Try everything!