The most venomous jellyfish in the world is the box jellyfish. We don’t have any in Ireland though, they are mostly found in tropical countries in the Pacific Ocean like Australia and the Philippines. If you were stung by a box jellyfish you would be in a serious amount of pain! You might get a headache and feel sick and all of your muscles will begin to ache you also might start finding it difficult to breathe. In very serious cases you could have a heart attack. People have died after being stung by a box jellyfish because they didn’t seek treatment straight away. As soon as you are stung by a box jellyfish you need to go to hospital. Even if it doesn’t hurt that much to begin with, it might get worse and you could be in serious trouble.