What Divers Should Know About Crinoid

Picture a creature that seems to dance with the currents, its many feathery arms unfurling like an underwater fireworks display. These are Crinoids, often known as feather stars or sea lilies, ancient marine invertebrates you're likely to spot on your dives. While some sea lilies remain anchored by a stalk in the deep, most living crinoids divers encounter are the free-swimming feather stars, gracefully clinging to coral heads or rocky outcrops in shallow water. Their defining feature is the array of five arms, which often subdivide into ten or more, giving some species up to 200 delicate, feathery branches.

These elegant filter feeders patiently extend their numerous feathery pinnules, sifting the water for planktonic particles. Unlike their stalked relatives, adult feather stars use small, root-like structures called cirri to grip onto surfaces, but don't be surprised if they suddenly unlatch and glide to a new spot using those same flexible arms. Their ability to curl their jointed arms is a fascinating sight, often done in response to light or a diver's proximity, offering a unique, dynamic encounter on the reef.