As most snorkelers and divers know, there are plenty of things underwater that can sting you: anemone, jelly fish, scorpion fish, sea urchins to name a few. Of course, there is nothing particularly special about the underwater environment that produces stinging creatures. Many land environments produce just as many stinging plants and animals. For example, the high desert canyon country of southern Utah where I live is chock full of cacti, spanish bayonet yucca, scorpions, spiders etc. And yet in over 19 years of exploring the desert backcountry here, it has been a very rare occasion that I or anyone I know incurs a sting.
On land, we are familiar with the plants and animals and easily identify those that might harm us. Also, we are used to accurately controlling our position and motion relative to the things around us. When learning to dive in a new place, almost every plant or animal we encountered is new to us. And to make matters more complicated, floating and weightless in water, it can take a little time to learn to accurately control our position and motion relative to stationary things like reefs and sponges and things that sting.
But with the help of our experienced guides, even our guests who are snorkeling or diving for the very first time acclimate quickly.
Staying safe while diving on the reef is mostly a matter of paying attention and learning which creatures to avoid touching. One that deserves special attention is the fire coral, so named for the sting it inflicts if a diver accidentally brushes up against it with his bare skin.
Fire corals are marine organisms that form colonies that look just like real coral but they are actually more closely related to the jellyfish family and other stinging anemones. One of the tricky things about fire coral is that it takes on a wide variety of forms. But all have certain characteristics in common, such as their mustard color and white tips, that make identifying them easier. Here is an excellent short article on the variety of fire coral forms and how to spot them.