When we were on the boat a couple years ago there was Asian lunch at Parrot Cay. They had a sushi spread in the middle of the restaurant but I'm sorry to burst your bubble... it was awful.
They tasted like grocery store prepackaged sushi rolls. The rice was awful and they used fake crab meat. I don't know if we were just unlucky on a sailing with bad sushi...
Hopefully they've improved it for our upcoming sailing... if they still have it.