The Lake That Sits Below the Sea

Inland from the coast the road climbs a dry pass, drops, and then there is water: a great pale sheet of it lying in a valley between two mountain ranges, with cactus and thorn scrub growing right down to the edge.

This is Lago Enriquillo, the largest lake in the Caribbean, and it is a strange one. Its surface sits more than thirty metres below the level of the sea, which makes this valley the lowest place in the region. The lake has no way out to the ocean. Rivers run in, nothing runs out, and everything the sun lifts off it leaves as vapour and leaves behind as salt. At its saltiest the lake is close to three times as salty as the sea.

The reason is written into the rock around the shore. Walk the low ridges near the water and you find coral in them, and shells, sitting in dry grey stone under the cactus, a long way from any beach. This valley was a sea once. It was a channel, open at both ends, joining the Caribbean to a bay on the far side of the island. Then, about a million years ago, a river laid down enough mud and gravel to close the western end. The strait became a lake, and the trapped water began to dry.

Polly walks a bank of that fossil coral with the heat coming up off it. The lake in front of her is flat and still and the colour of milk. Then something out in the shallows moves, and it is far too long to be a bird.