What prevents scuba divers from going deeper than 40 meters below the surface?

The pressure of the water and the feeling of being suffocated

As you go down, there is more water pressure pushing down on you.

It's like how if the football drops and the whole team jumps to get it and you just happen to get crushed on the bottom. The pressure of the other players will most likely break at least something in your body.

I'm just guessing that if you go lower than 40 meters, then there might be so much pressure, that they might die.