Their tentacles can be up to 190 ft long, with a bell diameter of almost 7 feet wide, they rival the size of the Blue Whale, the largest animal in the world. They live mostly in the Arctic and North Pacific Ocean, where the water is cool. However, they are attracted to areas affected by human activity. Overfishing, pollution and climate change reduce the numbers of their predators while increasing their prey.
Lion's Mane Jellyfish may occasionally drift into the Baltic Sea, but they cannot breed there (due to low salinity or salt levels). Similar jellies, which may be related, have also been found around the seas near Australia and New Zealand.
They have a one-year lifespan, or a little less, but in that time they can grow to massive sizes as noted above due to always eating as they drift in the ocean. They feed on zooplankton, small fish, moon jellies and ctenophores (comb jellies).