Marine iguanas eat algae — the slippery green and red plants that grow on underwater rocks. To reach their food, they dive into the cold Pacific Ocean and use their strong, flattened tails to swim like crocodiles. Some can dive more than 10 metres deep and hold their breath for up to 30 minutes.
After a swim, marine iguanas are cold and sluggish because reptiles cannot warm their own bodies from the inside like mammals do. So they crawl onto the black lava rocks and bask in the sun to warm back up. Their dark colouring helps them absorb heat from the sun quickly — like wearing a dark jumper on a sunny day.
When a marine iguana has taken in too much salt from the seawater, it sneezes the salt out through special glands near its nose. The salt sprays onto its face and dries, sometimes making the iguana look as though it has a little white crusty hat. It looks funny but is a brilliant bit of natural engineering.
Male marine iguanas can be quite colourful — some have patches of red, green or turquoise — while females are mostly dark grey. During the breeding season, males bob their heads up and down to communicate with each other. Galápagos iguanas are so comfortable around humans that they will walk right past visitors without any worry.