I dove the Blue Hole a couple of years ago. It's a long day that starts about 6AM, about a 60 mile boat ride, 3 dives (1st @ the BH as you really need to go to 135+' to get under and between the stalactites), and a return of about 6PM. Most people find the other two dives better, that it is indeed a long day, would probably not do it again (been there, done that), and are happy to have the T shirts to show for it. Having said all that, I think it's worth doing once.