The second of these films on the ecology of Sri Lanka looks at the life-sustaining lakes of the country, most of which were man-made during the reign of the ancient Kings of the country.
The island actually has two monsoons, but certain parts of the country see only one, and it is here mainly that is became necessary to build one of the foremost ancient hydraulic civilisations.
This has had an enormous effect on the ecology of the island, and helped protect many species, which adapted to rely on the water provided by these artificial works.
The film looks at the elephants, leopards and alligators which are using these resources, and the interlocking lives of the creatures they live with.
As always with National Geographic there is some wonderful photography giving access to the lives of creatures we would only ever glimpse otherwise.