Irukandji
The Irukandji is the most poisonous animal in the world. It is a jellyfish that belongs to box jellyfish species. The Irukandji became famous due to the death of swimmers in recent years.
It can be found in Northern Australian waters. In diameter, it is 2.5 centimeters. On its bell, are singers and tentacles. With such a length, it becomes a herculean task to detect the Irukandji in water.