Under the Sea wall display- blue butcher paper, kids paint blue waves in the ocean, use manila paper for the ocean floor. You can glue sand to the manila paper. Make all kinds of ocean animals. Some examples I used are below:
Octopus- 8 finger prints with paint then paint a circle on top. Glue googly eyes.
Jellyfish- Fill baggie with a little hair gel and sparkles. Tape on streamers for tentacles.