Jellyfish, with their undulating umbrella-shaped bells and sprawling tentacles, are as fascinating and beautiful as they are frightening and dangerous. They are found in every ocean at every depth, and they are the oldest multi-organed life form on the planet, having inhabited the ocean for more than five hundred million years. In many places they are also vastly increasing in number, and these population blooms may be an ominous indicator of the rising temperatures and toxicity of the world's oceans. Jellyfish presents these aquarium favorites in all their extraordinary and captivating beauty. Fifty unique species, from stalked jellyfish to black sea nettles, are presented in stunning color photographs along with the most current scientific information on their anatomy, history, distribution, position in the water, and environmental status. Foremost jellyfish expert Lisa-ann Gershwin provides an insightful look at the natural history and biology of each of these spellbinding creatures, while offering a timely take on their place in the rapidly changing and deteriorating condition of the oceans. Readers will learn about immortal jellyfish who live and die and live again as well as those who camouflage themselves amid sea grasses and shells, hiding in plain sight. Approachably written and based in the latest science and ecology, this colorful book provides an authoritative guide to these ethereal marine wonders.