I think the absolute best place is Mangel Halto, just a little south of the desalination plant. It's not as easy to get to as Malmok or Boca Catalina, but it has an incredible coral reef. If you are going to do Malmok I reccommend going late in the afternoon as the sun really lights up the coral at the at the bottom of the cliffs just below the water line allowing you to see a lot more.