Iguanas on the Galapagos are either land or marine iguanas. Both are about the same size, growing up to about 5 ft (1.5m), have stocky heads, a ridge of spiny scales along the neck and backbones. Land iguanas are lighter in color, tan to dark brown, and have shorter scales on the backbone.
Marine iguanas warm themselves in the sun, then dive into the water to feed on algae until their bodies cool and they surface to warm up again. They do this several times a day, but spend most of their time sunning themselves. They are equipped with special glands which allow them to drink sea water and expel the salt. Land iguanas are inland, lesser in number, and feed on cactus.