Here is some info on bioluminescence from wikipedia:

Bioluminescence has several functions in different taxa. Haddock et al. (2010) list as more or less definite functions in marine organisms the following: defensive functions of startle, counterillumination (camouflage), misdirection (smoke screen), distractive body parts, burglar alarm (making predators easier for higher predators to see), and warning to deter settlers; offensive functions of lure, stun or confuse prey, illuminate prey, and mate attraction/recognition. It is much easier for researchers to detect that a species is able to produce light than to analyse the chemical mechanisms or to prove what function the light serves.^[17] In some cases the function is unknown, as with species in three families of earthworm (Oligochaeta), such as Diplocardia longa where the coelomic fluid produces light when the animal moves.^[24] The following functions are reasonably well established in the named organisms.

We hope you enjoy this cool video and if you get a chance to see these organisms in person, look quickly before they disappear!

thanks to newscientist.com for the great info