"The animals are drinking water."
Translation:Les animaux boivent de l'eau.
Apparently this d'eau usage is very exceptional.
Even after reading an explanation of its use I still don't understand why it is used here.
In the example that I have seen d'eau is used to show possession by what the water is in. eg: a glass of water, a jug of water. The glass or jug possesses the water.
There is nothing in the Duo multiple choice example to show possession by a container, pond, stream, lake etc.