Simple Water from a material

Make a landscape from a plane and soft-selection:

The water is a box:

This is done only with creating a material, so the box segs can be 1x1x1. Here is you material; the diffuse color is 2, 3, 0, a really dark green.

Just 2 maps in Bump and Reflection:

The reflection slot is a fall-off with raytrace:

Amend the falloff mix curve ...

So far we have a nice glassy surface that picks up the mountain edges and the environment map sky:

Next for some ripples; the bump map uses smoke; here are the settings [size .04, iterations 20]:

Here is your render: