Answer: Lion’s Mane

Earth’s oceans are vast and packed with some pretty huge creatures, but we tend to associate behemoth sizes with creatures like sharks, whales, and such—the heart of a blue whale, for example, is as large as a small golf cart (weighing 400 pounds/180 kilograms). Floating out there in the briny depths, though, are some absolutely monstrously-sized jellyfish.

While some of them are large, to be sure, like the portly and aptly named barrel jellyfish that looks like a bright blue futuristic ottoman, there’s a clear winner in the contest for biggest in class: the lion’s mane jellyfish.

The lion’s mane jellyfish is so large, in fact, that it is considered a top contender as one of the longest animals on Earth. The largest specimen ever observed washed up on the shore of Massachusetts Bay and had a bell 7.6 feet (2.3 meters) in diameter and tentacles that stretched out to an astounding 121.4 feet (37.0 meters) long.