The Colentrata are a very common and diverse group, which includes the hydroids, jellyfish, sea anemones,
sea pansies, gorgonians and stony corals.
Colentrata are unique in possessing stinging cells called nematocysts, with which they immobilize their prey.
Hydroids may be found on almost any firm substrate-rocks, pilings, shells, boats, buoys, crabs and seaweeds.
Although hydroids are very common,
they are usually overlooked by the casual observer because they are small and look like plants.
Jellyfish, or medusa, are generally much larger than hydroids, but they are difficult for the
landlocked naturalist to see unless they wash up on the beach.
Sea anemones are common on the jetties, where they are often disguised by a covering of shell fragments,
and on oyster reefs and hermit crab shells. Sea pansies are found offshore on sandy bottoms.
Although they occasionally wash ashore, they are most often observed in trawl samples.
Gorgonians (sea whips and sea fans) may be found on the jetties below the water line or attached
to rocks or large shells offshore. Stony corals generally prefer warmer water than is found on
this coast during the winter.
Well developed coral reefs may be found offshore at the Flower Gardens Bank (19 Species), but only one species
lives nearshore, on rocks or other solid objects.
Most of the Caribbean has 55 species of reef building corals.