The jellyfish "Aurelia aurita" is common in all the seas and oceans of the globe, from the equator to the poles. It evolves in a large layer of water, from the surface to 120 m deep. From a height of 10 to 12.5 cm, the diameter of adult blue jellyfish can reach 40 to 50 cm. However, the most frequent specimens measure 15 to 30 cm.
The species periodically infests beaches, to the greatest terror of bathers, hence the common expression "year of jellyfish".
In nuclear power plants by the sea, where tons of hot water are discharged there, swarms of aurelias are frequent. They may be responsible, because of their number, for clogging the suction strainers. In addition, reductions in fishing catches can be observed locally, due to the massive predation of the fry by juvenile jellyfish.
This jellyfish is considered harmless. Typically, the aurelia sting is mildly itchy, but it can be felt very differently depending on the individual, ranging from null symptoms to a small superficial inflammation that does not last much more than two hours.