Speaking of sharks on a night dive, one of the best ever for me was in Turks & Caicos n board the Aggressor liveaboard. It was over Rock 'n' Roll reef and the chef/divemaster, my buddy and I were the only 3 divers. There was a bit of a delay in jumping off the boat by which time it had drifted unnoticed by everyone so that we wre now over the wall rather than on top of the reef's 'roof'. My buddy and I kept glancing at each other as best as we could in the dark as we descended but when the promised sea bed at 18m did not materialise, I checked by guage to find that we were at 24m and going down! We later discovered that another couple abandoned the dive as a result but Stacey and I acsended slowly to see what had happened. At 10m the chef swam past beckoning to us and we soon ended-up on top of the reef. From then on all we could do was keep turning in one place to watch as much of the action around us as possible. There were these huge blue jacks darting about at unbelievable speeds while several nurse sharks vied with them for food. Fish and crustaceans were all over the place and at one point I swear that a nurse shark swam through practically between my legs! We saw pufferfish, queen angelfish hiding in nooks, huge ornate lobsters, turtles, moray eels etc. It was like floating in space between critters instead of stars. To date that is the second most exhilarating night dive that I have done. Really unforgettable.