The 8 most peculiar sea creatures

By Becky Crew, Shannon Verhagen and Tim Low 28 August 2017
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From the fish that live in the anuses of sea cucumbers, to the crabs that wear sponges as hats.

AUSTRALIAN OCEANS are home to some of the most peculiar sea creatures, always intriguing us with their bright colours, elaborate sizes or bizarre behaviours. Here are some of our personal favourites. 

Feather stars

These strange, plant-like creatures hide in plain sight among bright corals and anemones, firmly anchored to the sea floor, as their slender, branching limbs billow like colourful fern fronds.

But things get positively weird when they break free ­­­– swimming, floating, or even walking through the ocean like a tiny Triffid that’s yet to realise its apocalyptic agenda.

feather star

This feather star looks a lot like an underwater flower (Image Credit: Tracey Jones)

Ox-eye oreo

Eespite that rather disc-like body, which looks like it’s been drizzled with a thick coating of burnt caramel, the curious little ox-eyed oreo (Oreosoma atlanticum) was not named after a dessert.

Rather, Oreosoma actually means ‘mountain body’, because if you turn one upside down, you’ll get a perfect little snow-capped mountain range.

ox-eye oreo

An ox-eyed oreo specimen. (Image Credit: Sandra Raredon/Smithsonian National Museum of Natural History)

The bubble snail

If there was a sea snail version of Cinderella, this would be it. It’s basically just one big magical glass slipper supporting a perfectly pink shell with careful patterns running along its lovely smooth curves. Meet Micromelo undatus, otherwise known as the miniature melo.

This elusive sea snail is found throughout the Indo-West Pacific and Atlantic Oceans, including off the coast of the US, South Africa, Japan, Thailand, and in very rare cases, Australia.

bubble snail

A ‘bubble snail’ doesn’t fit into its tiny shell. (Image Credit: Steve Childs)

The megamouth shark

The megamouth shark (Megachasma pelagios), with its blunt head —even larger than its abdomen, is one of the most unique species of shark to roam the depths of the ocean.

Only one has been reported form Australia — the third ever found, which was located in Mandurah, Western Australia in 1988. The shark washed up on the beach alive and was then collected and preserved by scientists from the Western Australian Museum.


The megamouth shark displayed in the Western Australian Museum. (Image Credit: the Western Australian Museum)


This slender, transluscent and scaleless fish really takes advantage of being pencil thin. Not content to make its home in the seabed or the crevices of rocks, it lives in the body cavities of invertebrates such as clams, oysters and starfish. And a notorious few reside exclusively in the anuses of sea cucumbers.

Pearlfish‘ is the common name of the Carapidae family, which includes 31 species of fish found in tropical waters all around the world, including off the coast of every Australian state except South Australia.


A pearlfish emerges from the anus of its sea cucumber home. (Image Credit: Richard Fitzpatrick)

Sponge crab

Chances are you’ve never spotted a sponge crab (Austrodromidia octodentata), but if you had, you wouldn’t be forgetting their wacky appearance any time soon.

While other crabs rely on their hard shells, intricate patterns and pincers for protection, these crabs use live sponges – fashioning them to their body and holding them in place like colourful hats.

sponge crabs

Sponge crab, Austrodromidia octodentata. (Image Credit: Karen Gowlett-Holmes)

Orangutan crab

Found in the tropical waters of the central Indo-Pacific region, including off the coast of Indonesia, the Philippines and Japan, the orangutan crab (Achaeus japonicas) is only small, with a carapace that measures just 2cm across.

From its eyestalks to the tips of its very long legs, it’s covered in a rusty-red coat of fine hairs. This shaggy pelt earned the species its common name, derived from the Indonesian word oran hutan, meaning “forest person”. If the orangutan is the forest person of the land, the orangutan crab is the forest person of the sea.

orangutan crab

An orangutan crab rests on some bubble coral. (Image Credit: L. Galko-Rundgren)


Found only in Australian waters, handfishes have stood out as oddities ever since French mariner Nicolas Baudin wrote in 1802 of a fish in Tasmanian waters whose “foremost fins are exactly like hands”.

They come in strange colours and shapes. The red handfish (Thymichthys politus) is blood red and the cockatoo handfish (Pezichthys amplispinus) has a fin like a feathered crest. Handfishes are like anglerfish in having an illicium, a spine like a fishing rod with a lure on top to attract prey close to their big mouth. Too slow to chase prey, handfish need it to come to them.


The endangered spotted handfish. Handfish are small, bottom-dwelling fishes that would rather ‘walk’ on their pectoral and pelvic fins than swim. (Image Credit: CSIRO)