Adding bump maps to water will increase realism by adding ripples to the surface of the water. Review the images to the right for examples of bump maps
Here are some examples using Wrinkled or Rubble procedural maps.
Bump Map Settings
These are examples of different settings of bump maps using the Wrinkled Procedural Bump Map to create a water effect. Notice how the sky and building are reflected in the water.
The larger scale would make more sense for larger bodies of water.
For more information on Bump Maps: