Coral reefs -- diverse, productive ecosystems -- found in shallow, tropical waters -- reefs formed from calcium carbonate (limestone) exoskeletons of corals -- crevices and caves provide shelter from many different plants and animals -- sponges, echinoderms, fishes.
(Coral reefs; found; L:in shallow, tropical waters) (crevices and caves; provide; shelter)
Coral reefs crevices and caves
found provide
L:in shallow, tropical waters
shelter