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Nudibranch -

Nudibranch, marine mollusks commonly known as sea slugs, rank among some of the most colorful critters in the ocean. Pictured here is an especially vibrant example, the wonderfully named Spanish shawl nudibranch.

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Mantis shrimp -

The psychedelic mantis shrimp may look cute, but believe it or not this crustacean packs the strongest punch of any creature in the animal kingdom: their club-like appendages accelerate faster than a bullet out of a gun to clout prey absolutely senseless.

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Christmas tree worms -

Christmas tree worm is the common and rather apt name for a marine worm that lives on coral reefs all over the world. The worms' most distinct features are two "crowns" shaped like Christmas trees that appear in all sorts of bright and festive colors.

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Coconut octopus -

The coconut octopus appears as if its tentacles are studded with sparkling rhinestone. The handsome cephalopod is named after its habit of collecting coconut shells for use as shelters.

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Blue tang -

Recognized for their characteristically vibrant colorations of royal blue and canary yellow, tang fish have a deadly weapon—a pair of razor-sharp, venomous spines on either side of their tails that they raise when in danger of being gobbled up by predators.

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Brittle star -

Closely related to starfish but infinitely more ornamental in appearance, brittle stars are possessed of five long, slender whip-like arms loosely coordinated by a nerve ring in the animal's core.

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Leafy seadragon -

These fragile and delicate creatures resemble the dragons of medieval fairy tales. Their earthy coloration and leafy appendages afford them excellent camouflage on kelp-covered rocky reefs.

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Flying gurnard -

When the flying gurnard gets excited, perhaps at the prospect of a snack or a shindig with its buddies, the fish spreads its "wings," which are fringed with a phosphorescent bright blue coloration at their tips.

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Flower hat jelly -

Flower hat jellies only live a few months, so catching a glimpse of one these guys is a treat indeed. This fluorescent jelly has lustrous tentacles that when fully extended resemble strands of braided hair set under a beret.

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Clownfish -

Ah, the clownfish. Star of Disney Pixar's 2003 film 'Finding Nemo' and its 2016 sequel 'Finding Dory,' this banded superstar is also known as the clown anemonefish for its clever arrangement with sea anemones, which protect it from predators.

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Red mesh starfish -

The red mesh starfish always looks as if it has lost a battle with a jar of strawberry jam.

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Banggai cardinal fish -

The elegant Banggai cardinalfish is known only from the Banggai Islands, an archipelago located off the far eastern coast of central Sulawesi, an Indonesian island east of Borneo.

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Mandarin fish -

These tropical beauties have scale-less bodies in blue, green, or orange-red, with a wavy pattern that creates a trippy psychedelic impression.

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Blue dragon -

A species of nudibranch, the ornate blue dragon is a stunning creature. Incredibly, among its favorite food is the dangerously venomous Portuguese man o' war.

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Discus fish -

The dainty discus fish is native to the Amazon River basin and celebrated for its spectacular kaleidoscopic coat.

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Parrotfish -

This group of fish species is daubed with splashes of vibrant color in the same patterns as their airborne namesakes.

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Green sea turtle -

The good-looking green sea turtle carries with it one of the most strikingly patterned shells of any turtle species.

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Regal angel fish -

The regal angelfish is undoubtedly one of the most vivid and striking saltwater tropical fish found anywhere in the world.

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Feather star -

A member of a family of marine animals known as crinoids, the feather star sprouts beautiful plumage, in fact a crown consisting of a cup-like central body known as the theca, and a set of five rays or arms, usually branched and feathery.

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Flamingo tongue snail -

Attractive as it may be, the flamingo tongue snail is actually an active parasite that lives and feeds off coral. Its body is akin to a wedge of pistachio nougat.

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Spotted eagle ray -

Sleek and graceful, the spotted eagle ray is the only ray commonly seen in Bermuda. They are named as such for the peculiar shape of their snouts, which are round and pointed at the tip.

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Long-snouted seahorse -

Known throughout much of the world as the long-snouted seahorse but in Great Britain as the spiny seahorse, this bewitching little creature ranges in color from black to yellow, red, orange, and brown with multiple white dots usually on the tail.

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Harlequin shrimp -

With its white body of large, light blue spots, the harlequin shrimp is easily recognized, though their favorite food, starfish, apparently don't associate the color scheme with danger: the hapless echinoderms are easily picked off.

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Red lionfish -

This venomous coral reef fish is classified in many regions of the world as an invasive species.

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Lagoon triggerfish -

This fish wouldn't look out of place in a Picasso painting. Besides its cubist veneer, the lagoon triggerfish has been studied for its remarkable locomotion. It can move forwards, backwards, or simply hover in place above a reef.

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Crown-of-thorns starfish -

One of the largest starfish species in the world is so named for its resemblance to the biblical crown of thorns, the color of which is also associated with events surrounding the crucifixion.

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Immortal jelly fish -

Exquisite, almost celestial in appearance, the immortal jelly fish is just that. This is the only animal in the world able to hit the reset button when faced with an imminent threat. It does this through the cell development process of transdifferentiation, which alters the differentiated state of the cells and transforms them into new types of cells.

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Sea spider -

Sea spiders are lanky marine arthropods whose stilt-like legs appear longer the deeper they are found.

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Gorgonian wrapper -

The gorgonian wrapper is a species of sea anemone named not for the creature in Greek mythology with hair made of living, venomous snakes, but rather because of its habit of attaching itself by its base and wrapping itself around the branches of gorgonians, the coral-like sea whips and sea fans.

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Enypniastes eximia -

This is a rare sight indeed, a fuchsia-colored deep-ocean sea cucumber first sighted in southern waters in 2018. Okay, so it's not going to win many beauty contests, but Enypniastes eximia's ethereal simplicity as one of Earth's newest species is hard to ignore.

Sources: (Harvard College) (Scientific American) (One Earth) (American Museum of Natural History) (Global Biodiversity Information Facility)

See also: Nature's most colorful creatures

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