Acid rain has a terrible effect on water life. Even if the acid rain does not fall straight into the lake, for example, it may enter from rivers and streams. Some of the life in the lake such as fish and plants may end up dying, because they cannot survive in acidic lakes.
Thousands of lakes in Scandinavia have no more life in them. They have received so much acid rain for so many years, because of the winds pushing the acid gases, that nothing can survive.
You can recognise a lake dead from acid rain by its clean and crystal clear water. But they look clean because there is very little living in them anymore. Tiny plants and animals are mostly unable to survive.