This is an extended deck of cards, with the usual red and black suits plus two more blue ones.
There is a long history of six-suited card decks. In 1895, Hiram Jones added Bullets and Crosses. Other designers have added Rackets and Wheels, Crowns and Anchors, or Valentines and Kites. The Blue Sea Deck stands in that long tradition.
Here the fifth and sixth suits are the blue suits of Stars and Squids. You can use the deck for playing Bridge with six, for making the odds in Poker go haywire, or for tossing card by card into a top hat.
The deck consists of six 13 card suits, 3 jokers, and a few information cards. It does not include rules or an actual squid.