public void setUseRefraction(boolean useRefraction) {
        this.useRefraction = useRefraction;
        if (material != null) {
            material.setBoolean("UseRefraction", useRefraction);
        }

    }
set to true to use refraction (default is true)

@param useRefraction true to enable refraction, false to disable it
(default=true)
jme3-effects/src/main/java/com/jme3/water/WaterFilter.java