A sea cucumber is a soft-bodied marine animal that lives on the ocean floor and looks more like a lumpy vegetable than any kind of fish. Despite the name, sea cucumbers are animals, not plants. They're related to starfish and sea urchins, though they don't have the same spiny appearance.

Sea cucumbers spend their days slowly crawling across the seafloor, using tiny tube feet on their undersides to move. They eat by scooping up sand and mud with tentacles around their mouths, digesting any bits of dead plants and animals they find, then expelling the rest. In this way, they're like the ocean's cleanup crew, recycling nutrients and keeping the seafloor healthy.

Some species of sea cucumber have a startling defense mechanism: when threatened by predators, they can eject some of their internal organs to distract the attacker, then regrow them over the following weeks. Others release sticky, toxic threads that can entangle or poison enemies.

In parts of Asia, sea cucumbers are considered a delicacy and are dried, cooked, and eaten. They've been harvested for food for over a thousand years, and some species are now endangered due to overfishing.