Azarial
But if you are going to make 13 more cards for the cups, you need to rely on more then just water. Is it a tarot deck or a bunch of pretty seascapes? You may know what it means to you, but there is a universal visual aspect I believe you may be ignoring. Maybe change the name of the suit to the sea or something.
Actually I did change the name of the suit to the sea. But it's hardly fair to assume that every one of the remaining 13 cards is going to be just a picture of the sea just from seeing one card.
-Pamela