Thumb loops............................A couple of weeks ago I was doing some training at Lake Wazee in Wisconsin. Water temps about 39 at depth. Even before starting the dive(while waiting for another diver to gear up) my thumbs felt numb. Like they were froze. Did the dive, had a h*ll of a time doing skills, frozen hands.
After the dive I walked over to my instructor asking if he had any idea what I might do.(Always get cold hands, but this was worse) He looked at my hands, see the thumb loop over my thumb and said "I bet that's the problem". Sure enough, that was it. I have latex wrist seals and when I push my hand though, I was inadvertently pulling the loops tighter and tighter around my thumbs.
Next dives that weekend, no where near as bad.
Just something to keep in mind. Al
P.S. Now I just pull a bit of undergarment under the seal.