Along the volcanic shores of the Galápagos archipelago, jagged fields of black basalt meet the relentless swell of the equatorial Pacific Ocean. Here, perched precariously on wave-swept cliffs, lives the world's only truly marine lizard: the marine iguana ( Amblyrhynchus cristatus ). While terrestrial squamates universally avoid prolonged immersion in cold seawater, this remarkable reptile has evolved an entire suite of behavioral, morphological, and physiological specializations that allow it to graze upon submarine pastures of macroalgae. First observed systematically by Charles Darwin during the voyage of the HMS Beagle, the marine iguana was initially described with a mixture of revulsion and scientific intrigue. Darwin termed them 'imps of darkness,' repelled by their flattened snouts, rough dorsal crests, and habit of sunning themselves in sprawling, lethargic clusters on midnight-black volcanic stone. Yet beneath this rugged exterior lies an exquisite evolut...