Also known as: カツオノエボシ, 鰹の烏帽子, 電気クラゲ
A type of hydrozoan. It is an animal closely related to Jellyfish and resembles them in appearance, but it is not a jellyfish in the strict sense.
They float on the sea surface, inflating themselves like balloons. Their long tentacles bear nematocysts, making them dangerous even to approach.
When stung by them, one feels an excruciating pain akin to an electric shock, which is why they are sometimes called electric jellyfish.