We wouldn't be surprised to find that sea angels are in the same family as, say, the mythological Sirens. They're called angels, but are actually a predatory sea snail. This particular specimen, Platybrachium antarcticum, "flies through the deep Antarctic waters hunting the shelled pteropods (another type of snail) on which it feeds," according to the Marine Census of Life.
There's no other snail in the world armored like the Crysomallon squamiferum, which was found over a hydrothermal vent deep in the Indian Ocean. The multilayered structure of the shell is called "unlike any other known natural or synthetic engineered armor."
One of the few known octopods known to be bioluminescent (glow with its own light) this Stauroteuthis syrtensis octopus was found about a half mile deep in the Gulf of Maine. Photophores (light-emitting organs) may be positioned to fool prey into swimming right into the mouth of the hunter.
Flamingo Tongue Snail
With a name like Flamingo tongue snail, and the flamboyant coloration to match, you might think that this Cyphoma gibbosum has a shell worthy of collecting. Not so. All its color comes from the soft parts of its body, which envelope its shell unless it's threatened. This specimen was photographed feeding on soft corrals near Grand Cayman in the British West Indies.
It lives in Monterey Bay and is called the vampire squid (and it appears to deserve the name). What else do you need to know?
The Dumbo Octopus
This Grimpoteuthis octopus found over the Mid-Atlantic Ridge, is affectionately called Dumbo because of the way it flaps its ear-like fins to swim.
Golden Lace Nudibranch
Something like a snail without a shell, nudibranch molluscs are known for their bright colors. This golden lace nudibranch, Halgerda terramtuentiss, was collected in the waters of the Northwestern Hawaiian Islands.
Hydrothermal Vent Snail
Another hydrothermal vent snail, this Alviniconcha snail was found at the Suiyo Seamount of the Tokyo Hydrothermal Vent. It's the only individual of its kind ever discovered.
Jewelled Umbrella Squid
This jewelled umbrella squid, Histioteuthis bonnellii, is found a mile deep or deeper above the mid-Atlantic Ridge.