The Great Blue Hole of Belize is the largest underwater sinkhole in the world. With about 100km of depth, its wonders still weren't discover because humans do not have machines able to go down there. Only professional scuba divers can dive in the Great Blue Hole of Belize, but for that they need to face some practice and simulations, so that they are prepared to face the cold waters of Belize.
Picture taken from here.
I read about the Great Blue Hole of Belize as one of nature's most incredible pieces of art. I love swimming which is one reason I would enjoy going there, and also the view there might be beautiful, both under and over water. Also, there are many wonders that still weren't discovered there, and it would be cool to swim in a place almost untouched. Some boats sinked there so there might be antique and unique objects there I'd love to try finding.