Upon encountering the great floating masses of sargassum during his first voyage to the “West Indies,” Christopher Columbus feared the weed was so thick and tangled as to forever ensnare his ships. For ages, the Sargasso Sea has been shrouded in both myth and mystery, fascinating scientists who are intent on unlocking its secrets and striking fear into most others. According to some romanticists, the Sargasso became known as a sort of marine hell, where ships and their crew meet a cruel fate. While early cultures viewed the vast expanse of the Sargasso Sea with trepidation, it would—along with its pinwheel of current—become the sea highway linking Europe and the Americas, facilitating exploration, colonization, and commerce. Generations of scientists have explored the Sargasso, unlocking a number of its secrets. One of the most startling revelations was that this sea is one of the great biological deserts of the earth—an oceanic badland of clear, blue water. And yet within this desert are oases of life. As Ulanski reveals, the drifting sargassum has been rightly compared to a tropical rainforest because it is a haven of biodiversity, where numerous species—from tiny larvae to small fish to juvenile sea turtles—take up residence in the sargassum's maze of stems, fronds, and floats. There is also growing recognition of the crucial and vital roles which the Sargasso plays in the wider North Atlantic ecosystem. Cloaked in myths, including weed entangled ships, sea serpents, and the Bermuda triangle, the Sargasso remains our most inscrutable sea. Blending history and anecdote, science and legend, geography and nostalgia, Ulanski tells the story of the Atlantic's sea, setting it against the backdrop of humankind's intellectual evolution.