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I believe that's a Ctenophore or Comb Jelly. The light you're seeing from the animal is simply light diffracting or scattering off its cilia and likely not bioluminescence (see http://perso.fundp.ac.be/~jpvigner/BioPhotonics/beroe.pdf and Ctenophores - some notes from an expert).This one is a clip of one of those luminous things. Can anybody enlighten me as to their appropriate name? You can see it here.