Coral atolls start out as reefs growing around the edge of an old underwater volcano. Over thousands of years the reef builds up, the volcano slowly sinks, and what is left is a beautiful ring of coral sticking just above the sea. Tuvalu's atolls are so flat and low that the highest point in the whole country is only about four metres above the ocean - about as tall as a basketball hoop.
Because the islands are so small, the people of Tuvalu are experts at using every bit of space. Funafuti, the capital island, is shaped like a long thin necklace of land - in some places you could almost throw a ball from the lagoon side to the ocean side. Coconut palms grow along the edges and their fronds rustle in the breeze all day long.
The coral reef surrounding each atoll is full of colour. Parrot fish, triggerfish, and hundreds of other species weave in and out of the coral. The reefs act like underwater gardens, giving fish a place to feed and shelter. Tuvaluans have fished these reefs for generations and know them like a neighbour's garden.