The art of painting with water is a complex one, with the secrets of mastering it lying in how you mix the colours, your strokes when applying them and also the addition of water in creating a gradient around your subjects.
While in the process of creating a water colour painting, most artists hate it as the look of it never quite signals how it should look like when its completed. So simply ignore the work in progress and trust your instructor on how it'll turn out in the end! It almost always turns out well :)
Note: Bring your own drinking water