Pelagia noctiluca

Pelagia noctiluca is a jellyfish. In Latin, "Pelagia" means "of the sea", "nocti" stands for night and "luca" means light thus "Pelagia noctiluca" can be described as a marine organism with the ability to glow in the dark. 
This species is commonly known as the mauve stinger. It occurs in warm and temperate waters of the world's oceans, including the Mediterranean Sea, Red Sea and Atlantic Ocean. It is also found in the Pacific Ocean, with sightings in warm waters off Hawaii, southern California and Mexico. 
It is an offshore species, although sometimes it is washed near the coastlines and may be stranded in great numbers on beaches. The color varies. As well as pink or mauve, it is sometimes shades of golden yellow to tan.
In an unprecedented event on November 21, 2007, a swarm of jellyfish wiped out a 100,000-fish salmon farm in Northern Ireland, causing around £1 million worth of damage.
As its name implies "P. noctiluca" has the ability to bioluminesce, or produce light. Light is given off in the form of flashes when the medusa is stimulated by the turbulence of a ship’s motion or by waves. This flashing is short, and gradually fades.