Leak under in floor of van

I have a 1999 Olds Silhouette. We've only had it 18 months. It has about 125,000 miles on it. 7 passenger. Lately we've noticed the carpet in the floor of the drivers side, just back from the pedals towards the seat, is very wet. At first we thought it was a spill, but it does not go away. It stays very wet and seems to be slowly getting bigger. Any idea what could be causing it? Someone suggested a/c may be leaking. Is that even possible? Never seen a leak inside a vehicle. Thanks so much.