The Okavango is a delta with no coast: the river comes out of Angola, fans across the sands of the Kalahari in northern Botswana, and ends there. What makes it strange is when the water arrives. The rain that fills it fell in the Angolan highlands months earlier and creeps across the fan at about a kilometre a day. The flood peaks in the middle of Botswana's dry winter. By then the sky has been cloudless for months and the delta has doubled in size. The land is at its driest exactly as the water peaks, and every animal for a long way around comes in to it. The way in is a mokoro, a dugout canoe poled from the stern, riding centimetres above the surface.
From that height the delta closes in to reed walls and lily pads, and with no engine you are among the birds before they notice you. More than 400 species use it: storks in the reed beds, bee-eaters flashing past the hull, a fish eagle dropping off a dead tree. Elephant families ford the channels in single file, calves walled inside the herd, close enough that you hear the rumbles between them. The water also splits the herds: on the islands, game drives find buffalo and antelope that swam to get there, and lions that have learned to swim after them. The delta holds one of the largest surviving populations of African wild dogs, found by their tracks and by other animals' alarm calls. At first light the pack greets itself in a frenzy of tails and whines, then fans out across the floodplain. None of it makes sense until you get above it. From a small plane off a dirt strip it resolves into a silver web of channels, islands and lagoons, with desert running up to the water. The elephants keep the same calendar as the flood. They scatter over the drylands when the rain comes and fall back onto these channels as everything else dries out, so in the driest month of the year you find them standing in water.