A small purple-brown jellyfish that appears in large numbers in the Mediterranean and eastern Atlantic.
A mushroom-shaped bell to about 12 cm, mauve to red-brown, with warts of stinging cells over the bell itself as well as on the four oral arms and eight tentacles. Touching any part of it stings, which is unusual.
It arrives in swarms, sometimes for weeks at a time, and is the commonest cause of stings in the Mediterranean. The sting is sharp and can leave a mark for days. It is not dangerous to a healthy adult, but a face full of them on a safety stop is a genuinely unpleasant dive.
A hood and a full suit deal with most of it. When they are running thick, the sensible decision is often not to dive rather than to dive covered up.
This entry carries no occurrence record. The animal is listed because it is a hazard a diver should be able to look up, and its range is given above, but none of the destinations this site holds data for is inside that range. A record will be added when there is one to add rather than an estimate to invent.
