BELIZE // As every mountaineer must ascend Everest, so too are scuba divers drawn to the depths of Belize's Blue Hole Natural Monument. Jacques Cousteau charted the hole's depth at 124m (407ft) in 1971, declaring it one of the world's top scuba sites. From above it looks like a perfect, 305m (1000ft) blue circle but when divers drop in, they descend past ancient, storeys-high stalactites hanging from the roof of the underwater cave. The lucky ones catch a glimpse of a Caribbean reef shark or two, and maybe even a hammerhead. From the bottom of the hole, light from above is but a pinprick, towards which divers resurface slowly and with great care. Snorkellers can glide around the reef-covered rim, encountering small fish and the occasional turtle.