The marine iguana feeds on seaweeds that grow on rocks in the intertidal zone and beneath the surface. Large males can dive to feed, and they can stay under water for considerable amounts of time. Like other diving animals, marine iguanas have evolved special physiological adaptations like slowing their heart rate and directing blood flow to the most vital parts of the body. Historically, sailors who visited the islands in earlier centuries found the appearance of the marine iguana to be repugnant. Darwin called them "imps of darknes."