The technique to get all sorts of fun coral reef pieces and designs is called Hyperbolic Crochet, and this is what I have crocheted so far...
The following links are my inspirational photos for the types of looks I want to go for: Crochet Coral Workshop and Crochet Coral Reef.
Hyperbolic crochet is a type of freeform crochet that involves using lots of increases and any of the four basic stitches (sc, hdc, dc or tr) that strikes your fancy. It is a form of crochet that can really inspire you to get creative, use your imagination and even beginners can do it!
If you would like to learn the basics of hyperbolic crochet, here are a few resources that I have been using: Hyperbolic Crochet Motifs by Lion Brand Yarn and How to Crochet Hyperbolic Corals by the Institute for Figuring (It can be downloaded as a PDF).
Have you ever tried Hyperbolic Crochet?