what if

[wowenglish1]

I wonder if there is any difference between "1" and "2".

He saved a drowning woman.
1. What if he didn't jump in? Her life would have been lost.
2. What if he hadn't jumped in? Her life would have been lost.

[5jj]

Only#2 is appropriate.

#1 is not possible. The first sentence refers to a hypothetical present or future non-jump, the second to a past counterfactual loss of life.