You can never know completely how a large body of water will freeze. I remember once going out to fish on a small lake in Alberta Canada, the ice close to shore was over 12" thick. I was walking out to a favorite spot when I noticed that about 100 yards ahead the area seemed to be open water. I carefully and quickly put a 90 degree turn on and went to shore. I followed the shore around to the open area which was indeed not frozen at all almost all the way to shore. I put the ice auger to work drilling holes and checking the depth and was able to get close enough to cast into the open water to fish for trout. Had a good day also. A week or so later I was back again and that spot had 12" of ice on it. I had been fishing that lake every year for 3-4 years and never had I seen that spot not frozen at least 12" by the time fishing season opened (except that one time). The water depth there was about 25 feet. My partner and I were fishing there once when the ice was about 8" which Canadians say is plenty thick to drive a car on and while sitting on our fishing buckets, cars would drive out and we could feel the pressure ridge rising several yards in front of them. For us is was like a miniature roller coaster ride. The water which is usually an inch or more below the top of the ice would rise up and flood out of the hole when they came driving along several yards from us. Kind of creepy feeling, almost as much as having an expansion crack shoot between your legs when those things happen. First time I heard that rifle crack sound it scared the crap out of me not being familiar with what was happening since Ark/La/Tex area doesn't have anything in the way of ice fishing.