I don't know about you, but when the instructor points out in bold print in the book the part that says you go deeper than this and tox you die, that's something you remember. I feel that diving it will NOT imprint the fact you can die, but seeing it and having the instructor reinforce it multiple times will allow you to remember it.
If a person is incapable of remembering the fact that it's possible to die, then diving 2 times is not going to imprint it either. Consider the fact that what's more valuable than your own life? If you can't remember something important where it's stated in bold print and verbally that you can die, and most likely will if you tox then diving is not for you. How stupid can a person be?