Like other land animals that have adapted to life in a marine environment, sea snakes swallow considerably more salt than their relatives living on land. They do this through their diet and when they inadvertently swallow sea water. Kidney function in birds and reptiles is too weak to remove enough salt. In birds, such as penguins, salt is removed through nasal glands. The marine iguanas of the Galapagos Islands use the same mechanism. Sea turtles have lacrimal glands that allow them to produce very salty tears. But in sea snakes, glands under and around the tongue let them expel salt with their tongue action.