A Warning from the Shore: The Danger of “Dead” Jellyfish

One of the most surprising and important biological facts about jellyfish is that their ability to sting does not end when they die. The nematocysts on a jellyfish’s tentacles can remain active and capable of firing long after the jellyfish has washed ashore and perished.

This means that touching a jellyfish on the beach, even one that appears to be long dead, can still result in a full, painful sting. The firing mechanism of the nematocysts is an automatic, cellular-level reaction to pressure and chemical cues; it does not require the jellyfish to be alive to function.