Postcard from the Reef – Hydroid Stings

This is not a case of “I wish you were here”, but rather another lesson in the many hazards of diving.

Hydroid Stings
The welts left behind by hydroid stings across a forearm one day after the injury

I know when I got hit, a series of pricks down my left forearm. I didn’t even react, I was concentrating on the photo. I continued to brace myself against the surge by using the rocks of the cave floor. Those rocks were home to some little critters that had an issue with the disturbance I was creating… Hydroids.

Through the rest of the dive my arm continued to sting, discomfort that persisted but was not really all that bad. I took no action other than noting that I had gotten hit. It wasn’t until the next day that I realized that the stings were not going to go away quickly. I had a series of red welts across my forearm, and they itched. Time to break out the hydrocortisone cream. A week later the welts have faded and shrunk to pinpoints, no longer itch, but are still there.

Hydroids
An unidentified hydroid hanging off a lobe coral (Porites lobata) Kohala Coast at about 70ft
The angry red welts did attract comment all week, they were rather noticable. I have had to explain what hydroids are a number of times. These small relatives of jellyfish posses the same defensive armament, stinging cells called nematocysts. As soon as you mention jelly stings the stories come out, most everyone on this tropical island has gotten stung at some point.

Friday evening we stopped into the shop of Kohala Divers for a bit. There were a few folks we know in the shop as they were having an open house. As I chatted with Lina Preskitt, a local marine biologist, I mentioned the stings, showing her my forearm. She raised her forearm to display a very similar set of red welts on her left arm! We laughed as we looked at a mirror of almost identical stings.

This is the second time I have been seriously stung by hydroids. Will it stop me from diving? Not at all. Perhaps be a bit more careful when mucking about on a cave floor.

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on the island of Hawaiʻi.

2 thoughts on “Postcard from the Reef – Hydroid Stings”

  1. perhaps a long sleeve wetsuit would help?
    Nice pictures tho so it was worth it to us for you to sacrifice your self
    Aloha
    Dan

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