Pin the Fin on the Fish
This party game adds a fish twist to the traditional "Pin the Tail on the Donkey" game. Draw a large picture of a fish on poster board. Leave off one of the fins or the fish's tail. Draw that part of the fish on a separate piece of paper. The kids are blindfolded and each takes a turn trying to place the fish's fin or tail in the right spot. The child to get the closest to the correct spot wins the game.
Go Fishing
There are several versions of a fishing game you can play with the kids. The basic fishing pole structure is the same no matter how you play the game. A long dowel creates the pole. Tie some fishing line or string to the end to complete the pole. You'll also need to tie either a paper clip or a magnet to the end of the line depending on how you want to play the game. One option is to have an adult hide behind a couch with paper fish cutouts. The child goes fishing by swinging the line over the back of the couch. The adult places a fish on the paper clip at the end and tugs the line. The child then retrieves the fish. Another option is to put several fish cutouts in a kiddie pool or box. Each fish should have a paper clip on it. The fishing line has a magnet tied to it so it can pick up the fish.
Shark Tag
Shark tag is ideal for outdoor parties. One person is the shark and tries to catch the other players who are the fish. Any player who is tagged then joins hands with the shark to form a larger shark. This continues until all of the fish are caught. If the shark becomes too large, divide the shark players into two smaller sharks. Keep dividing the shark group as necessary.
Flipper Relay
This relay game incorporates the underwater theme. You'll need a set of flippers for each team as well as a swimming mask. The first player on each team puts on the flippers and the mask. The players then race down the length of the playing area and back to the start while wearing the underwater gear. The gear is passed to the next person who repeats the process.