Coral is a strange and wonderful thing. It looks a bit like a rock or a tree, but it is actually made up of millions of tiny animals (called 'polyps') all living together. Each polyp builds itself a hard little cup, and as new ones grow on top of the old, the reef slowly gets bigger - one millimetre at a time.
Seychelles is right in the middle of one of the world's richest sea areas. There are over 1,000 kinds of fish, big and small. Parrotfish chew at the coral with beak-like mouths. Clownfish hide in the swaying tentacles of anemones. Hawksbill turtles glide between the rocks looking for sponges to eat.
Reefs are very fragile. They need clean water, the right temperature, and to be left alone. When the sea gets too warm, corals can lose their colour and turn ghostly white - scientists call this 'bleaching'. People in Seychelles work hard to look after their reefs, replanting young corals in places where the older ones have been damaged.
Seychellois schoolchildren often go on snorkelling trips with their classes. They are taught to look but not touch, to watch where they put their feet, and to take only photos. Many kids in Seychelles know the names of more fish than the names of pop stars.