Researchers have built a robot crab that can compete in claw-waving displays with real fiddler crabs, but "Wavy Dave" doesn't always come out unscathed.

What are the blue blobs washing up on California beaches? What to know about these strange sea creatures.

The newfound ecosystem is filled with sea crabs, octopuses and gigantic sponges, suggesting it may have been thriving for centuries.

A shortfin mako shark, the fastest-swimming shark in the world, was caught on camera with an octopus catching a ride on its back off the coast of New Zealand.

The mantis shrimp's club uses a built-in vibration shield that filters out damaging shock waves to enable it to strike with bullet-like force without breaking.

Giant phantom jellies were discovered in 1899 and since then have only been spotted around 120 times.

A growing body of research suggests crabs, lobsters and other animals caught for seafood can feel pain. Scientists are pushing for legal protections to ensure they are treated humanely.

A never-before-seen predatory crustacean that feeds on other smaller creatures in the hadal zone was discovered in the Atacama Trench at a depth of 25,900 feet.

Researchers exploring the seafloor off the coast of Chile recently captured mesmerizing footage of a flying spaghetti monster — a carnivorous, colonial creature with countless milky-white arms.