The flower-hat jellyfish Jellyfish first appeared about 650 million years ago and are found in every ocean, from the surface to the deep sea. Some are also found in fresh water Medusa (plural medusae) is another word for jellyfish.
Flower Hat Jelly - Olindias formosa - Occurring in the West Pacific off southern Japan, this jelly is of the family Oliniidae. It can grow about cm) in diameter. The sting is painful and powerful enough to leave a rash, but it is not deadly to humans