A very small box jellyfish whose sting is mild at the time and produces severe symptoms half an hour later.
A transparent bell about the size of a thumbnail, with four tentacles. It is effectively invisible in the water and is usually not seen at all, before or after.
The sting itself is minor. What follows, after twenty to forty minutes, is the reason it is listed here: severe back and muscle pain, sweating, nausea and a rise in blood pressure. That delay is the important fact for a dive plan, because a diver can surface, feel almost nothing, and be seriously unwell by the time the boat has moved on.
It occurs in northern Australian waters, and similar species occur elsewhere in the tropics. A full-length suit covers the exposed skin that gets stung. Anyone who becomes unwell half an hour after a swim in that region should be treated as a medical case, whatever they remember or do not remember feeling in the water.
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.
