Box sea jellies (Carybdea branchi) are common in Cape waters, and we sometimes see great swarms of them. They are characterised by a roughly cubic bell, with a single tentacle emanating from each lower corner. The tentacles may be retracted at will (if you touch one by accident, the tentacle shortens), and the jellies seem to extend them further at night – possibly for feeding purposes.
It is these trailing tentacles that can, it turns out, deliver a nasty sting. I have swum too close to a box jelly before, and where its tentacles touched my exposed face I felt as though I’d been splashed with hot water (actually not a wholly unpleasant experience on a cold dive). Within a few minutes the sensation was gone, and no marks remained when I came out of the water. On a night dive at Long Beach in July, however, I had a proper experience of how these jellies can sting.
I didn’t even notice the jellyfish as I swam around the wreck, but suddenly became aware of an intense stinging sensation around my neck where the top of my wetsuit meets the edge of my hoodie. We were only ten minutes into the dive, so I put it to the back of my mind and continued swimming. The pain was still there when I exited the water, and became more intense as my skin dried. I rinsed off in fresh water at the beach, and we headed home. The lower half of the front of my neck was an angry red colour with raised white welts. More rinsing in warm fresh water, and then an application of (not joking) some All Stings Considered gel that Tony bought in Durban ages ago did little to dull the pain.
It was a full three days before my neck stopped looking and feeling angry, red and lumpy. Tony reluctantly sent me off to the office – wearing a scarf, lest my colleagues think he strangles me in his spare time. As the sting healed it progressed to looking like a severe case of adult onset acne. We washed my hoodie, wetsuit and rash vest thoroughly to make sure that no stinging cells remained on them, because they can retain their stinging power for some time. Unfortunately not thoroughly enough, because the following weekend when I put on my wetsuit I was stung again, quite extensively – in the same spot on the front of my neck, and also around the back. Time to washing machine the wetsuit!
Fortunately our box jelly is nowhere near as venomous as some of the varieties found in Australia and Indonesia. I very much doubt that anyone has died from a South African box jelly sting. That said, if you’re the sort of person who reacts violently to things and often needs antihistamines, I’d take care to avoid exposure where possible. The NSRI has a fascinating explanation of the stinging mechanism and a run down of some of the treatment options here.
We are actually very fortunate that there are very few ways to get stung in Cape waters. The odds of a sting when one wears so much exposure protection are very small. The other frequent stinging culprit is the bluebottle, which tends to affect swimmers and those strolling on the beach more than it does scuba divers. Don’t hate the jellyfish!
