Well To make a long story short my '05 SS has a wet drivers side rear foot well. At first I was pissed because I was leaning back to fish out a CD, but It was soaked, I mean puddle soaked. So I stopped and checked to see if I left a water or drink on the floor, but there was nothing. I went straight to my dealer to see about getting it checked and they knew all about it. Apparently I'm the 3rd car at that dealer that has complained this week alone!
Some pro guy is coming on friday to look at the others so mine will be in that day too.

Anyone hear of this??

 

I had that happen only a little on my 05 base coupe. I have not had that problem on my 06 ss/sc

 

I Have a 2005 Cobalt SS/SC Red, Bought New in August 2005. With less that 4,000 miles on it we had the Passenger side front footwell FILL up with water while driving (several inches of standing water. It turns out that there was some defect in the Heater box that was allowing the A/C drain to be re-directed to the inside of the vehicle. Took into the Dealer and they performed a "Heater A/C update" where they basically repaired and resealed the Heater box. This fixed that problem, of course they left my coolant low which gave an intermittent low coolant light that required a trip back to the dealership. Don't know if this is related to your problem but hope it helps