I created a pattern of something like what Asharads result looked like, by offsetting by half the image size, then used the clone stamp tool to fill out the blanks. Then, Define Pattern. On the picture I've just painted in some green, used Pattern Overlay (multiply, 60% opacity), and then used a Bevel and emboss on it, to give it some distinction from the water. But the Bevel and Emboss has nothing to do with the pattern itself.