They usually spread the decks out durring the sail out to the 3 mile limit. Some cruise ships allow the players to sit at the tables as they count and check the cards, while others do not allow players into the casino area until this is complete. I always felt this was weard because getting to certain tables you need to be the frist one there or you get locked out.

It is also not uncommon for them to use broken sealed decks of cards on some cruises.