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Meet the Giant Samoan Crab

From time to time while scuba diving in Kauai I come across a true monster that looks like it should be in a Star Wars movie! This huge crab was introduced into Hawaiian waters in the 1920s and can grow to an amazing 15-inches wide from the tip of one massive claw to the other.

Most people only see the Samoan Crab on the dinner plate as it is a delicacy on many tropical islands but if you have ever swam in a beautiful Hawaiian stream below a lovely waterfall you have probably swam right over one!

The Samoan crab is in the family of Hawaiian swimming crabs often known as kuhonu. But what is very unusual about this large crab is it can live in fresh water and salt water. When you drive by a river mouth you often will see buoys that mark fishermen crab traps and this is the crab they normally catch in the muddy river water.

The back legs of the Samoan crab are modified into paddle like fins that allow the crab to swim backwards swiftly. When approached by a predator or diver, the crab will walk backwards with it claws extended.

If the predator gets to close the crab may lock onto the predator with a powerful grip that can tear right into a persons hand or a shark’s nose. If that does not work, the crab can release its grip and swim quickly backwards to hide in the reef or hau bush that lines the river mouths.

These large crabs use their claws to tear up bits of dead animals if finds on the riverbed and out on the reef and also to eat algae. I have seen more of these crabs at the mouth of the rivers in the bays where dead plants and animals wash out to sea to offer them some food.

While scuba diving one day in a bay here in Kauai I came across one of these Star Wars looking crabs that was participial buried in the sand and I only saw its top part of the shell. When I got close to get a better look it bolted up out of the muck and spread out its massive claws!

The first thing I did was to make sure my metal underwater camera was between me and this crab monster! The crab locked onto the metal frame of my camera and I could hear the grinding until it let go and scurried away!

It torn the yellow paint right off of my underwater camera housing and I was just glad it was my housing that suffered the damage and me!

You can see the Samoan crab in action in my new video, “The Worlds Guide to Hawaiian Reef Creatures,” up on my underwater educational web page at

Aloha from under the waves,


Terry Lilley, Marine Biologist, Hanalei,,, All Photographs © 2016 Terry Lilly
Source: The Garden Island

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