It was about 20 minutes or so, but we were probably in the water for close to an hour. Due to the cold, we were having some difficulties getting going.
I had used my rig earlier in the day doing a pool session with students at the shop, so my reg and BC were still damp. As soon as I set my rig up, everything stiffened up from the moisture freezing on my BC and my reg began to freeflow. The only way to loosen everything up was to get into the water to let the 34 degree water melt the 32 degree ice. Once in, I turned on the tank valve and voila, the freeflow problem was fixed and I was able to tighten my straps. Freefloat's octo holder literally froze and we had problems putting the octo in.
All told, we farted around in the water a good 20 minutes or so before going down.
Brrrr.