Only a few of the intertidal creatures, like the marine iguana and Sally Lightfoot crab, will be familiar to most visitors, but if you take a close look at life on the tidal rocks and in the tide pools, you will discover an ecosystem every bit as complex as that on land. Most of the creatures that live in the intertidal zones are invertebrates and there are many hundreds of species. These amorphous, variously colored blobs are really animals that filter out minute plants and animals from the water. You'll also find sea anemones , related to the corals, hydroids and jellyfish. Starfishes, brittle stars and sunstars are a familiar group.
Most species are predatory, eating mollusks and the like.
Starfish are often brightly colored and can regrow their limbs, if lost. Two species of sunstar, Heliaster spp., are common in intertidal areas. Just as starfish can eject their stomach to start the external digestion of a mollusk, so sea cucumbers can eject and abandon their lower intestine and other entrails when disturbed. Like the lizard's tail, these regrow. Due to recent marine harvesting by Asian entrepreneurs, sea cucumbers are extremely endangered.