Fish and shellfish are foods from the earth’s other world, its vast water underworld. Dry land makes up less than a third of the planet’s surface, and it’s a tissue-thin home compared to the oceans, whose floor plunges as much as 7 miles below the waves. The oceans are voluminous and ancient, the “primordial soup” in which all life began, and in which the human imagination has found rich inspiration for myths of destruction and creation, of metamorphosis and rebirth. The creatures that live in this cold, dark, dense, airless place are unmatched among our food animals in their variety and their strangeness.