The lion's mane jellyfish is the largest in the world, longer than a blue whale. The ones in the Arctic are the longest types, while the ones in the North Equator were smaller than a book. Lion's manes in the North grow to no more than about five inches, but the long lion's manes can reach lengths of up to one hundred twenty feet, it's tentacles possibly longer than a blue whale. Swimming straight trough a huge jelly in the Arctic can prove fatal to a diver, though it's still very cold there. The bell(body of a jellyfish, not the ringer) can sometimes be as large, though likely wider, than an average person in America. The largest bell of a lion's mane ever recorded was a stunning seven feet in diameter, when discovered off the shore of Scotland.