The Nomura jellies that have plagued Japan in recent years are big, yes – 450 pounds and seven feet long, roughly the proportions of sumo wrestlers. But they are petite compared with the lion’s mane jellyfish. This cold-water species can reach over 100 feet long. Granted, most of its length is tentacles, but that’s no cause for relief – the flowing appendages pack a nasty punch. Indeed, this jelly emerges as the murderer in a classic Sherlock Holmes short story, “The Adventure of the Lion’s Mane.” Although the lion’s manes are often found farther north, the giant jellies are reportedly gracing the shores of Holmes’ native England this summer.