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Found in Australia, this jellyfish's venom is 100 times more powerful than a cobra's. It is especially common in Queensland, north of Cairns. Being the smallest jellyfish in the world - only half the size of a penny – there are jellyfish nets set up to ensure safe swimming areas on the beach to keep Irunkandji out.
The bite can be treated but if it isn't seen by a doctor quickly, it can be fatal. The symptoms of the Irukandji syndrome become more and more intense within about half an hour of the bite and usually nausea, vomiting, anxiety, severe pain throughout the body, an increased heart rate, blood pressure and sweating.