Many thanks for your responses. When I was docked two shots for hitting the wrong ball, it didn't feel is if it was correct. For we had both entered the water at almost the exact spot and it was my opponent that scooped out the ball before I had time to to inspect it. I didn't realise he was playing a same make and number ball, although he had marked his with a smile and two dots, and I had marked mine with just two spots. I could see the two spots (the smile was out of sight) so assumed it was my ball and dropped it outside the hazard alongside my opponent and we both then hit our third shots. It was only when I retrieved my ball from the hole (having chipped in) he noticed the smile and announced I had hit the wrong ball and insisted I be penalised a further two shots.
My sincere thanks for your assistance.