That reg in the picture is a Atomic B2, with the cold water kit installed did not freeze on the first dive, just on the 2nd AFTER the dive. It is sealed. There is a diver with a sealed diaphragm, GT3, non-DVT and his froze also AFTER it had been out of the water. My reg is a Atomic B2 with seal and it has not froze up..yet, did not freeze after I got out of the water. My reg is the same as Troy's and was sealed at the same time. . The other piston reg is a Sherwood Oasis and has not froze either ( the instructor's) . The Aqualung Legend, diaphragm, froze also. I honestly don't know if any regulator could survive these extreme conditions, and the key is not to exit the water between your two dives of the day. The reg should never hit the air until you are ready to stop diving. I would have to say at the end of the day, the pistons did better than the diapraghms, overall. You have to remember it's 37 degrees in the water and 19 degrees in the hut. Sudden change doesn't do anything good.
There are so many things to think about, gear, exposure protection, restrictive movement, cold, ice, weight, lines, you name it.
We are going to try for UW pics tomorrow. There was just to much going on today.