In this tutorial, you will learn how to create a lake using Boolean operations.
If you don't know what Boolean operations are, you can read about them here!
(link to the Boolean tut)
However, it is not absolutely necessary for this tutorial. It's just an idea...

Start up Vue and create a new scene.
Choose any atmosphere and delete the 'Ground'.
Press the 'Terrain in Editor' button.

Press OK in the 'New Terrain Options' window.
Press the 'Filter Altitudes' button. in the 'Terrain Editor'.
In the 'Altitude Filtering' window, right click inside the 'Altitudes filter' section and select 'Edit Filter'.
You will load the 'Filter Editor' window.
Edit your filter similar to the picture below.

Select the 'Numerics' tab in the 'Object properties' window.
Highlight the 'Orientation' button and enter 180 in the 'Pitch' field.

Highlight the 'Position' button and enter 100 in the 'Z' field.
Create the 'Ground plane' (Objects > Create > Ground Plane).
Position the 'Infinite plane' like in my picture below.

Press and hold the 'Ctrl' button.
Select the 'Infinite plane' and the 'Terrain' in the 'World Browser'.

Press the 'Boolean Difference' button in the left toolbar. Try to render.

Now we need to pour water in our basin.
It is simple, just add water to your scene, and raise its position.
You can easily control the water level in the 'Numerics' tab.