When scouting out potentially thin ice for the first time, I only go maybe a few feet to a few yards at a time, before doing about 3 solid whacks with my chisel. If water fills in, I check closer. I also carry a long pole with me to assist in getting out if I do go through. I also dress to be prepared to go through. I generally feel acceptably safe with 2 good inches of ice. If I know it's shallow, I might take my chances. Once I establish safe areas, and then set locations on a swamp, I stay where I've already been and get to it.
I think being dressed appropriately and prepared to go through, if it happens is important. You wouldn't want to panic about it. Just get out and go to the truck...which I try to keep at close hand during the early season. I also would think twice about going on thin ice when it is really cold...10 degrees and windy and 30 degrees and not windy are too very different things. I figure the pole I carry will get me out. Beaver swamps are not usually so deep that a long pole wouldn't reach bottom and the water usually isn't moving. If it is moving stay away. I've heard of some with a pair of screw drivers and other things to assist yourself in getting out. Keep a complete change of clothes in the truck at all times. I've done a lot of white water canoeing, which happens to be best early in the spring. I've dumped as early as the first week end in March. I would recommend wearing duofold long johns, two pairs of wool socks, a pair of regular pants, flannel shirt, wool sweater, and then wool pants, a wool jacket, wool gloves, and a wool hat. Basically wool. That fancy new age crap isn't the same. Really cold water will take your breath away. The most important thing is to not panic.
