Jellyfish, siphonophores and stinging hydroids. Grouped by what they do to a diver rather than by relationship: these are the animals that sting on contact and are easier to swim into than to see.
The stinging hydroid is the commonest sting on a tropical dive and looks like a plant. The upside-down jellyfish lies on the bottom with its tentacles pointing up, farming algae in its own tissue, and is often in numbers in shallow bays over sand.
The serious ones are a short list. The Australian box jellyfish is the most venomous animal in the water anywhere it occurs; the irukandji is small enough to pass unnoticed and its effects arrive half an hour later; the Portuguese man o' war is a colony, not a jellyfish, and its tentacles sting after it is dead and on the beach. Local advice on season and protective clothing is worth more than any general rule, and the hazards page sets out what to do.
Every one has a page. They are shown as a list rather than as pictures because nothing has been photographed or logged for them yet, and a species with nothing behind it should not sit in front of one that has.
How many of the 10 carry a record at each destination. A species usually carries several, so these do not add up to 10.
All 1316 species in one index, with filters for destination, rarity and hazard.
