For my daughter's fifth birthday party she had an "Under the Sea" theme. We decorated the ceiling of our family room with different colored paper fish and different shades of blue crepe paper to represent water.  The fish hung down at different lengths as did the water. As the girls arrived, they found their "place" at the table by locating small bags of blue plastic wrap that contained Swedish Fish. They then had to color and decorate a fish tail cut from poster board.  These were later used to play "Pin the Tail on the Fish". I made a large fish on blue poster board and decorated the board to look like the ocean.  Each guest had to bring a pair of socks that we used to decorate with puffy paints. We were pretending that they were special swimming fins. We also went outside where my husband had placed crayons in the yard.  They were instructed to each go fishing for 6 different colored fish.  These were placed into bags I had decorated with fish stickers and their names. The bags contained small coloring books, also.  The last activity of the day was the fish pinata. We did not serve lunch, but we did have fish crackers for munching. I made the cake myself using a 9x12 cake pan and cutting the corners off of one side to use for the fins.  I decorated it with blue and yellow icing.  The fish scales were made with Necco wafers.  His eye was a peppermint patty and his mouth a small piece of licorice. The thank you notes were written on a notepad that was in the shape of a fish I purchased from the teacher supply store. Each thank you note also contained a picture of my daughter with each guest and the gift they gave her.  It was a great party for 5 year olds!