Agreed. You don’t see him flying in the air. Only the take-off and landing.
You do see “him” flying in the air and emerging from the pool, in a continuous take.
You lose sight of him at the trough of the slide. A figure appears on the upslope of the slide, flies through the air, lands in the pool. Then you lose sight of the figure behind the pool walls and a man emerge from the pool.
So maybe there were two different men at the beginning and the end, and a dummy flying through the air.
On the other hand, it looks like it might be in Norway, and they have some insane people who jump off cliffs in wing suits.
Watch it again, his arms are moving as he flies. I think it was faked though with some clever editing.
What video were you watching?