Take a $6 taxi ride to Cabbage Beach. Awesome waves, clean beach and not crowed at all. This beach is within walking distance to the Atlantis. ALso if you're into getting "hammered", you can get a coconut hammered in half and can drink for the rest of the day for $10. I didn't take them up on the offer because I was afraid of what "mickey" they may have put in the drink.
Be careful, the wave are big and very strong.