Nigaloo has some of the best scuba diving in the world, along with the nearby Navy pier. I actually prefer it to the Great Barrier Reef, as you don't need long boat rides, and can dive right off shore if you want. Its really common to take road trips up the coast from Perth with a camper van, and you can camp anywhere on great beaches near the road. Besides diving, they also offer whale shark tours where a small plane flies over head searching for the sharks so that you don't have to search all day by boat. Awesome place.