Underwater fireworks.

The rainbow zipper (Euplokamis) propels itself with tiny combs whose tightly spaced teeth beat against the water. The rainbow appears because the combs act like little diffraction gratings, breaking the white light into individual colors. When bumped and viewed with the lights out, the zipper releases a cascade of bioluminescent sparks as well as a steady glow from its comb rows.
http://www.tufts.edu/alumni/magazine/fall2007/features/oceans.html

http://docmo.hubpages.com/hub/Animals-that-Glow-The-Science-of-Bioluminescence

http://en.wikipedia.org/wiki/Ctenophora