Lion's mane jellyfish (Cyanea capillata) from underneath, seen against clouds in the sky. This is the largest known species of jellyfish. It can reach over 2 metres across with tentacles of around 30 metres long, containing millions of nematocysts (stinging cells). They range from Arctic waters to the coasts of Florida, USA, and Mexico. Photographed in the Russian Arctic, in the White Sea.