The Blue Hole in Belize was incredibly awesome. I did the dive at 140 feet with a 28% nitrox mix. There are tons of stalagmites creating an almost earie scene, all the while black tip sharks circle around you. Quite breathtaking but not for the faint of heart! If you stay on Ambergris Cay keep in mind that this is several hours each way by boat so, if you do not like long boat trips or you get sea sickness keep this in mind.
The cenotes on the Yucatan Peninsula of Mexico are pretty interesting. The water is pretty cold so make sure you have proper thermal protection and your gear is in good shape. There are ropes anchored along the walls and there should be a leader and an end person watching the group. As divers we are used to so many colors and a lot of life however, these cenotes are barren of any of that but interesting as you can see the thermoclines filtering into the caves which look like Vaseline in water and find air pockets where you can remove your regulator and talk, sounding like Mickey Mouse. Speaking of Mexico…best drift diving in the world is in Cozumel. You can stay in Playa del Carmen on the Riviera Maya, dive the cenotes, and then take a ferry to Cozumel to do some incredible drift diving.