Don’t be fooled by its poetic name or its tropical location: Dean’s Blue Hole is deep, dark and intimidating. But, if you’re up for it, you can tame the world’s deepest known seawater blue hole by learning to become a free diver.

You probably won’t beat William Trubridge, who broke the unassisted free diving record by diving 100 meters here in 2011. And you certainly won’t conquer all 203 meters of this light-and-oxygen-deprived sinkhole. But you’ll have a great time getting close.

You can stare into the faces of some of Australia’s biggest saltwater crocodiles for 15 minutes, separated by nothing more than a couple inches of glass.