Monterey Bay Aquarium has a brilliant YouTube channel for viewing all sorts of beautiful and hard-to-believe creatures. A case in point: these four jellies. Above, The Lobed Comb Jelly, who looks like it’s shimmering with neon lights.
These ctenophores (not to be confused with Cnidaria or jellyfish) diffract light from their locomotory cilia, producing a pulsing rainbow effect, “much like sunlight glancing off a CD” — iridescence (not bioluminescence).
You can see this spaceship-like quality in the fragile spotted comb jelly, too:
The Bloodybelly Comb Jelly video below is from 2009, 30 years after one was first collected off the coast of San Diego, California. They can be deep red, purple, or black, which may hide any bioluminescent prey that it eats, keeping it stealthy in dark waters.