>>10878170Only 3 feet of water is enough to stop a .50 cal antimaterial rifle according to the Mythbusters.
https://www.youtube.com/watch?v=yvSTuLIjRm8The human body is 60% water, so you need 5ft of human body to have the equivalent of 3ft of water.
However, I suspect that this is highly dependent on the geometry and mass of the bullet. A normal .50 BMG might be absorbed but an APFSDS for example with the same powder charge might not be.
