Snapping/Shocking Coral, Tiny Creature, or . . . ?

[hawkans]

I'd like to identify what it was that twice flicked or shocked me while snorkeling in Culebra, a small island off the coast of Puerto Rico. I believe in hands-off diving and snorkeling, but nonetheless there were some times where I had to pinch a portion of (coral-covered?) mossy, greenish rock or place a bare foot against it for support in a current while trying to photograph a small creature/etc. In the waters of two different beaches, something in the coral (or rock/moss) made a loud snapping sound and gave me what felt like a hard flick or electric-bug-zapper shock. The first time it happened was on the bottom side of my heel, and the second time, a day or two later, was on my pointer finger. It didn't cause any injury, but it did hurt a little. I have attached a screen shot of a photo I took, to give an idea of the environment.

 

[Doctorfish]

Nothing to see in the picture but from the description, I'd guess Pistol Shrimp.

Damsel fish are pretty good at taking small bites if you encroach on their turf, but that does not explain the popping sound. I wouldn't go stepping on the rocks again. You are lucky that's all that happened. Stone fish and Urchins can produce nasty injuries.

 

[hawkans]

Thanks for the input. I think your guess is the most likely answer, especially after reading others' descriptions of it feeling like the snap of a rubber band. World's Deadliest: Amazing Pistol Shrimp Stun "Gun"