From the box:
"A fabulously funny game of tropical fish trading!
Mr Plankton runs a crazy shop called Fishy Business. You've got to help him sell his weird and wonderful tropical fish, in particular the Outer Mongolian Mackerel, the Fantastic Finnish Flounder, the Brazilian Balloon Bloater and the Poisonous Tiger Trout.
Don't forget your fishing net!"

The winner is the player to get rid of all their cards first. Game play shares similarities with Uno, in that players play one card at a time from their hands, which must match either the same species as the previous card, or the same number. In addition, there are a selection of special cards which cause an opponent to pick up more fish from the pool, or which can be used to change species.