People have actually died in Jacob’s Well, but not just from jumping, you’re too buoyant to really go down far.
But Jacob’s Well draws a lot of scuba divers, and some of them have gotten lost and run out of air. Some of the bodies have never even been found, because the underground river that feeds Jacob’s Well is so complex. I find that terrifying.
I’ve been there. You have to be careful because coming back up from too far and you get stuck under rocks trying to find the surface.