You can't knock someone out under water

Right. Unless he was insanely strong and he hit him maybe going with the natural flow of the river and hit him in the EXACT right spot to make him disoriented. But I think we'll have to suspend disbelief for this one guys. lol

Don't be ridiculous! Jack would never die without telling me

that completly depends on how strong you are how and fast your fist is moving.

no it would only slow your strike down but any blunt force can knock you unconscious

I never thought that Wade was trying to drown Tom to get him out of the way, but you're more than likely right on that count. That makes great, good sense. Tom had to hit Wade to stop him.

Cool theory but incorrect. Wade couldn't swim so obviously he was panicking. He wasn't trying to kill the husband at such an early point because they didn't want to blow their cover yet. Nothing more complex than that.

I don't think it was explicitly stated, but I think the implication was that Wade can't swim. he was definitely drowning and panicked. there are other times where he's in deep water and moves very carefully not to let it get too deep (when anyone that can swim can just... swim). and when strapping Streep into the boat he says "I figure this puts us at the same level" because he can't swim.

He wasn't knocked out. The punch was totally unexpected and caught Wade off-guard. It wasn't as much the impact, but the disorienting nature of the act itself that caused Wade to momentarily loosen his grip, giving Tom an opportunity to swim up. At least that's how I saw it.