I would suggest you doing some reading on your own as to the proper method to bag a fish. As mentioned in article one below things like double bagging and transporting in a cooler are probably more important the worring about the water to air issue.
I won't turn this into a debate, but if you are trying to give your fish more oxygen the answer is more air not water. However I agree you don't want your fish to be rapped in a wet paper towel either, because having enough water to dilute any urination/waste so that it isn't raised to poisonus levels is also important.
Good luck and please let us know how things go.
Brandon
From an online article:
Fish are most likely to suffocate when the bag contains too much water. The volume ratio of air to water is more important under most conditions. Roughly, the bag should contain no more than 25 percent water. In fact, the great risk to transporting fish is not asphyxiation but 1) ammonia poisoning, 2) overheating or freezing, 3) leaks, 4) physical injury and 5) systemic stress from handling during the move.
From another online article:
When plastic bagging fish for transport, use only enough water to just cover the dorsal fin. Squeeze out the current air, add 5-10 times the amount of oxygen as water.