Echinoderms are a group of deuterostomes with more than 6,000 existing species and a high evolutionary status among invertebrates. Most sea cucumbers are benthic, and a few sea cucumbers live a pelagic life; free-living species can move slowly. They are widely distributed from shallow seas to deep seas thousands of meters deep. Starfish, sea urchins, sea cucumbers, brittle stars, etc. that are common along the coast are all echinoderms.