Lake Baikal

Polly woke on the fifth morning. The world had become water.

The train was running along Lake Baikal. The lake filled the whole window. The water was a deep, perfect blue.

Igor, the fisherman, was at the window with a notebook.

"Baikal," he said. "It is the deepest lake in the world. 1,642 metres deep. It is also the oldest lake. 25 million years old."

The water was so clear that Polly could see rocks on the lake floor in the shallow places.

"It holds 23 percent of all the fresh water on Earth that is not frozen," Igor said. "More than all the Great Lakes in North America together."

The train stopped at Slyudyanka station. Igor got off. He shook Polly's wing tip with two fingers. "Three days fishing. Then home." He waved and was gone.

The train ran along the lake for three more hours. A group of Baikal seals came up to the surface. They are the only freshwater seals in the world.

Polly thought about how much water was below her. A tiny pink shrimp lives in Baikal. It keeps the water clean. It has been doing this job for 20 million years.