I'm curious.
Suppose a pedophile kidnapped your child, and buried him somewhere with a limited amount of air left. The police catch the pedophile but don't know where your child is buried. The clock is ticking. The police try various ways to get information from the pedophile. They try pleading to his humanity, trickery, family contacts, sympathy, legal deals, etc. They know from his family that he's terrified of drowning (he even avoids crossing bridges).
Would you approve of using waterboarding on this person to get information?
Nope.