There's two dives that come to mind. Though I haven't dived much i'm lucky enough to have been to some pretty good Spots
SIPADAN: I stayed on Sipadan Island for three days, and it comes as no surprise that the diving here is amazing. As soon as you are in the water, just off the beach in Front of Borneo Divers you will see more turtles than you have probably seen in your life! 20 in one dive is normal.
The last dive of my stay was the best, a blue water drift. We started off close to the Island and soon we were drifting through a large school of Barracuda, then as we moved away from the island I spotted two Tuna, cruising effortlessly in the deep blue.
OSPREY REEF, CORAL SEA, FNQ, AUS:
This is my favorite place, the whole experience has a dreamlike quality.
My first dive there was the most memorable. From the surface, it didn't look like the vis was very good, there was quite a swell running and the conditions where choppy. As soon as I got my face in the water, I was blown away! I have never seen water that clear, except in a sinkhole. It must have been 75mtrs vis.The water was a deep, deep blue, and it was thrilling to think that the bottom was 1000mtrs below. Immediately I dropped down into a big school of barracuda, they swirled around me in a circular pattern. Grey Whalers and White Tips were everywhere, waiting to be fed. It was like floating in space, it was a surreal feeling that will be hard to repeat. I've got it on tape if anyone wants to see it.