If you are interested in crocheting as well as geometry and marine biology, this is really fun. Corals grow hyperbolic and this can be used in the art of crochet. You can crochet your very own coral reef.
I was introduced to this by my friend Irene from Ireland who teaches crocheting at yarnclasses.com
There are some amazing crocheted coral reefs out there travelling from exhibition to exhibition. The last one I heard of was The Toxic Coral Reef, where the corals are crocheted out of materials like plastic bags or video tapes.
Here is a picture of my own little coral