The marine iguana is the only lizard in the world with the ability to live and forage at sea and is endemic to the Galapagos Archipelago.

Marine iguanas are not a very agile species on land, but they are excellent swimmers - moving easily through the water as they feed on algae. Larger individuals go further out to sea and use their powerful claws to grip on to rocks in strong currents to feed, whilst the smaller ones stay inshore near rock pools, feeding on algae exposed at low tide. Due to the high concentration of salt in their diet, marine iguanas filter their blood at the nose and sneeze out the excess salt, often forming salt crystals on the snout.