Because all reptiles are cold-blooded, they must rely on behavioral means to regulate body temperature. Basically, the iguana just basks in the sun all day until it reaches its optimum body temperature of 35.5 degrees Celsius. Reaching a sufficient body temperature before swimming offshore is essential, since the iguana's body temperature can drop nearly 10 degrees while submerged. To conserve heat overnight, marine iguanas simply aggregate, or pile together, at dusk. Because of high salt levels in their diet, marine iguanas have developed particularly effective salt glands, located above the eye and connected to the nostrils via ducts.
Salt is removed by frequent sneezing, explaining the often salt-encrusted heads.