I've been fortunate enough to have been to some really nice places in my travel history (Hawaii, Pacific Mexico, Fiji, Jamaica, Bonaire, Kosrae, Antigua, Bora Bora, not to mention my local Channel Islands CA!), but by far the place which eclipses them all is Rangiroa in French Poly. My wife and I spent a week diving there and the wonder never wore off for us. We stayed at the wonderful Hotel Kia Ora (
http://www.hotelkiaora.com/home.php ) in an overwater bungalow and enjoyed the hotel's great food and hospitality in what is one of the most spectacularly beautiful places on earth. We dove with TopDive (who we loved in Bora Bora, but not in Rangiroa) and I would not recommend them ... opt instead for the far nicer and better equipped Blue Dolphins (
http://www.bluedolphinsdiving.com/index_eng.html ) .
Diving in Rangiroa is done through the two passes into the lagoon during the tide shift, primarily Tiputa. You dive off of a zodiac, which drops you outside the pass in the bluest ocean you could imagine. Usually the first thing you'll hear is dolphin calls and they appear out of nowhere to play with you. As you drift toward the reef you will see turtles, mantas, huge Napolean Wrasses, and sharks. We even sighted a hammerhead on one dive. As the current pulls you into the pass you look down and then you see them ... hundreds of sharks. More than you can hope to count! They look like ants swarming over each other below you (I shot a short vid that I'll try to post from high up so that you can see the enormous number of them but I know there are several on YouTube that you can check out). Then you notice that the current is starting to pick up, faster and faster as you move into the channel. You'll reach a speed of six to eight knots or so and you are absolutely flying! The world is passing you by so fast that there is no hope for you to swim against the current ... if you wish to stop and watch the sea life you'd better be close to something to hold on to. As you feel the current let up you are deposited into the lagoon, where you pop your SMB to let the zodiac know your location. I could do that dive a million times and never tire of it because each time we did it we saw different things. And you never get tired of seeing those sharks!!
Rangiroa is a huge atoll, only a small part of which is populated. We rented a scooter and rode from one end of the island to the other in about 20 minutes. There are a surprising number of good places to eat and there's even a winery on the island where you can stop by and do some tasting. The wine's OK, nothing earthshaking but how cool is it to have a winery on a tropical island?
I'm sure I'm forgetting many things but I wholeheartedly recommend it to be on anyone's "short list" of your life's dive destinations.