{OOC: Okay, lemme look this up right quick... The drowning rule in
the SRD I'm looking at is 2 rounds/point of Con. It makes no mention of exertion reducing the duration.
I just checked
the Swim skill - I remembered the drowning rule as 1 round/point of Con - and it says what you've got there. (Though, note, swimming is not exerting yourself. Only things like attacking [standard/full-round actions] count for that.) Presumably the former rule is for deliberate submersion and the swim skill rule for sudden, unexpected submersion. This was more the latter than the former, so I suppose it's a round/Con point. Still, that leaves a number of rounds left for even the weakest-lunged of us.
Something I noticed - the Swim skill seems to be thinking combat-type actions for the exertion clause, but includes full-round actions on the list, which includes swimming half your speed. Could you instead just do two move actions to swim? That seems odd for some reason, but you are allowed to take a move action in place of your standard action.
Ashy, if that makes sense, I've been taking two move actions instead of one full-round action every round. *cough* And next time I'm drowning I'll look it up right away.

}