Assets/Standard Assets/Editor/Water/WaterBaseEditor.cs(11,17): error CS0246: The type or namespace name `WaterBase’ could not be found. Are you missing an assembly reference?

This error pops up at my editor
How can i solve it?

There should be a script file somewhere called “WaterBase.cs”. The error message says that it’s missing, which really shouldn’t be the case with standard assets. Try to reimport the package.