Some things living on coral reefs are, indeed, poisonous. Some kinds of pufferfish, starfish, lionfish, sea urchins, and sea anemones could be poisonous if you tried to touch or eat them--and these animals all live on coral reefs. Coral, itself, is usually not poisonous, but if you scrape yourself on a piece of coral and get a cut, your cut could get infected and it would be pretty painful.

With all of these poisonous things, you might think that a coral reef is a scary place to be. This is not the case! Even though there are poisonous animals on coral reefs, they usually won't bother you if you leave them alone. Coral reefs are beautiful and incredible places to go swimming!

I've gone snorkeling in coral reefs, and I didn't get hurt. So coral reefs aren't poisonous, but there might be some poisonous animals and fish that live in some coral reefs.

Some species of coral do contain poisons.

The reefs are not poisonous, but the corals that make them are.