Please see Tutorial with step-by-step instructions and examples.
Version 1.2.1Compatibility issue fixed ( GIMP 2.6.7 )
Version 1.2 Changes: 1. Additional control over parameters: - 3D correction - Initial noise level 2. Option to decompose result into two layers image (separate X and Y) 3. Minor changes and optimization (i.e. now called "Water reflection map")
Based on idea from Photoshop Tutorial: Displacement Water