You could use a Fractal Noise (animated) layer as a displacement map to displace just the water area. You can use the same layer (duplicated) with the Levels crushed (to see highlights only) and Glow applied to it, comped on top with a Add or Screen transfer mode.
Another way would be to use FreeForm Pro to generate water using the AquaPack: http://www.mettle.com/aqua-pack/
[Tudor "Ted" Jelescu]"You can use the same layer (duplicated) with the Levels crushed (to see highlights only) and Glow applied to it,"
Agree with everything people are saying here, my 2 cents would be to do the fractal noise and if you have the 'Optical Flares' plugin you can set this to luminance mode and play with the threshold, this will flare wherever the 'water' is brightest. With a subtle scaled down flare to give a shimmer this should look cool.
Here's a free template that I put together that simulates water using the standard built in effects in AE and is great for still images. It simulates waves, not the glitter from the sunlight but you may still find it useful. PseudoNami Water Simulation Template