Jellyfish expert Lisa Gershwin caught the unnamed species in early March while swimming near a jetty off the Australia island of Tasmania with a "phototank"—a small aquarium that makes it easy to photograph sea life.
The jellyfish does not emit its own light, as bioluminescent creatures do.
Rather, its rainbow glow emanates from light reflecting off the creature's cilia, small hairlike projections that beat simultaneously to move the jellyfish through the water.
Though the glowing jelly is Gershwin's 159th species discovery in Australia, she still finds the discovery "simply splendid."
For one, the jelly is relatively large—5 inches (13 centimeters) long.
The new species also belongs to Ctenophora, a "strange and poorly known" group of animals, said Gershwin, curator of natural science at the Queen Victoria Museum and Art Gallery in Tasmania.
The invertebrate is also incredibly fragile—it shatters as soon as it touches a net, she said.