9. Box Jellyfish
The Box Jellyfish, mainly found in Australia, may seem harmless because of its transparent and small size. However, it is one of the most venomous creatures in the world. Its tentacles can extend up to 10 feet long, and its venom is capable of causing death within minutes if not treated immediately. The venom affects the nervous system and can even cause cardiac arrest. The best way to avoid this deadly creature is to avoid any contact with the water altogether.
