I haven't been to the "shark-infested" waters of Cocos or Galapagos (both are super-high on my list) but I was pleasantly surprised to see the sharks of Palau. It's obvious that what they're doing is working! On almost every dive we'd see sharks in the blue and cruising the walls. On the famous "hook-in" dives of Blue Corner and Peleliu, we saw at least a dozen sharks just hanging out with us in the current. I really hope that more countries follow this fantastic precedent!
Palau was the first country to declare their waters a sanctuary for sharks and as a result of their efforts the fish and turtle populations also seem equally healthy. Absolutely fantastic to see that their efforts are paying off with healthy reefs, healthy fish populations, healthy shark populations, and lots of turtles!
We dove Palau in July 2015 and dove with the Aggressor fleet - specifically staying on the Tropic Dancer. We'd highly recommend both the boat and the crew (Captain Ike, Photo Pro Ben, Chef Cameron, and absolutely fantastic DMs: Jonathon, Conor, and Jim).