Nudibranchs

Nudibranchs: Beautiful Animals You Never Knew About

I wouldn't suggest you actually read the text - the writing is so bad it might make you vomit your entrails like a sea cucumber (which, weirdly, aren't even in the same phylum as nudibranchs. so that joke doesn't work very well.). Just look at the photos.

Besides looking pretty, nudibranchs can do a lot of interesting things. Some of them eat hydrozoa (like jellyfish) and assimilate their stinging cells, and others eat plants and use the chloroplasts to photosynthesize food for themselves.