5. Box jelly
This guy wont kill you (most of the time) - just hurt you really, really bad. Theres a bunch of different sizes of box jelly, ranging from larger ones with tentacles 3 meters long and much smaller ones at only about 3 cm. Much like the blue ringed octopus and most cone shells, these are also found in the warm waters of the Indian Ocean. While some of them do grow quite big, its the tiny ones that you cant see you want to look out for. Annoyingly, the smallest are no bigger than a couple of centimetres and completely see-through. Good Luck with that. After being stung, (which you might not even notice because the sting itself isnt actually that bad) the pain will set in. The pain has been described by those unlucky enough to experience it as worse than death and all over your body. Although if youre lucky, you might just die on the spot instead if you get stung really bad or multiple times, as some species have enough venom to kill 60 adults. Symptoms usually last for about 30 hours, so theres a day in the sun youll never get back. Oh, right, and theres no anti-venom. There might be a trend here