Why doesn't anyone go over the Calm Belt? The Calm Belt has no oceanic currents so sailing a normal ship through it is impossible.
However, throughout the series we have seen ships that can sail without wind, such as Boa Hancock's ship that is pulled by sea kings. There are also plenty of Devil Fruit users that have an ability to get them across. A lot of people already travel the sea by themselves using their powers, like Kuzan, who can glide across the water, or even Buffalo that can fly over.
Why hasn't anyone thought to go over the Calm Belt instead of traversing the Grand Line? Is there something that presents that from happening?
Nobody goes though the calm belt because there is nothing important there and no reason to go there beside to go through the Grand-line. https://onepiece.fandom.com/wiki/Calm_Belt