This is Hanauma bay, it's a good snorkeling place to enjoy while you're in Oahu. Great opportunity to swim with the fishes and turtles. I think you have to pay $5 for kamaaina rate and I don't know how much for tourist.  I came here before but I'd rather swim with the turtles and fish at north shore by sharks cove. It's a little bit crowded but I saw more turtles and fishes up there. I rather do the Hanauma hike trail than swim in the ocwan.