Watch as a Crab Use Its Incredible Flippers to Shoot Through the Open Ocean

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Written by Chris Madden

Updated: November 10, 2023

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The blue crab - (Callinectes sapidus)
© Vojce/

Not Only Do Crabs Walk Sideways, They Also Swim Backwards!

In this captivating underwater video, a crab takes center stage. It defies its terrestrial reputation and showcases aquatic prowess. The camera seamlessly tracks the crab’s journey, capturing its distinctive maneuvering technique. Utilizing its previously concealed back flippers, the crab propels itself through the open ocean with impressive agility.

As the camera follows the crab, it elegantly glides backward. This reveals its prominent face and formidable crushing claws, all oriented towards the viewer. The scene transitions as the crab descends toward the sandy seafloor. Here, gently undulating sand patterns come into view.

Descending further, the crab assumes a resolute defensive posture upon landing. With unwavering courage, it raises its mighty claws. These are aimed against a perceived threat that’s vastly larger than itself, highlighting this crab’s bravery and aggression.

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This serves as a poignant warning, indicating the predator should retreat or risk a formidable pinch. The crab maintains its defiant stance while tactically retreating. It scuttles backward out of the frame as the video comes to a close.

Blue crab under water walking on sandy bottom

A beautiful Blue Crab puts its strong crushing claws in front of it, as a clear warning to any predator that they could get pinched!

©Jen Helton/

Is It Normal Behavior For Crabs To Swim?

While many crabs, such as stone crabs and spider crabs, typically move by walking or running along the ocean floor, there are exceptions within the crab family Portunidae.

These crabs have uniquely adapted back legs known as “swimmerettes.” These paddle-shaped appendages can rotate at impressive speeds.

Additionally, each side of the crab features a conspicuous, sizeable, and sharp spine. Between the eyes and the prominent spine on each side, you can find eight short spines. The pincers are notably larger, although one claw is slightly larger than the other.

Furthermore, the fifth pair of legs has a flattened side that helps the crab swim.

What Would Make a Crab Swim Through Open Waters?

In various aquatic scenarios, a crab strategically opts to employ its backflippers for swimming. This is instead of relying solely on its usual method of walking across the seafloor. When facing predators in open water, the crab swiftly unfolds its flippers. It propels itself through the water with remarkable speed and agility. This enables the crab to escape danger and find refuge in the depths.

Moreover, during migration, these flippers become crucial tools. They allow the crab to cover larger distances efficiently. In areas with strong currents or turbulent waters, swimming is a more energy-efficient mode of transportation.

This ensures the crab conserves its resources. Furthermore, when searching for food, the ability to swim aids the crab. It can explore diverse underwater habitats and seek out new sources of sustenance. These sources might otherwise remain undiscovered.

In essence, the decision to swim using its back flippers showcases the crab’s adaptability and resourcefulness. This enables it to navigate its underwater world effectively.

Flight of giant octopus

Octopuses are extremely intelligent and capable of breaking through the tough shell of a crab with its crushing beak, making it a lethal predator.


Of a Crab’s Many Predators, Which is the Biggest Threat to a Crab Swimming Through Open Water?

Crabs face an array of predators in their aquatic habitats. This shapes their behavior and survival strategies. Fish, octopuses, and seabirds are prominent predators targeting these crustaceans. When swimming, crabs might be particularly exposed to fish and larger marine organisms. These predators capitalize on their vulnerability in open water. The swift and agile movement of crabs through the water could draw the attention of these predators.

While crabs often utilize their backflippers to propel themselves and evade threats, the shift in environment introduces new challenges. This intensifies the predator-prey dynamic, underscoring the need for versatile survival tactics.

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About the Author

Chris is a lifelong animal lover with a passion for writing and a natural tendency to explore the internet in pursuit of new wildlife and nature facts! He is completing his Bachelors in Political Science at Concordia University in the Spring of 2024 after a science-centric high school career. Aside from studying and writing for A-Z Animals, he has a budding music career and enjoy spending time outside year-round, from swimming to skiing!

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