I grew up on an oxbow lake, about a mile long and a hundred yards wide. There is a very high bank on the outside bend of what used to be a river bank. About 90' up. All the water pressure in that high bank pushes down and springs pop up in the lake all along that high bank. Especially after heavy rains and heavy snow melts. The ice can be a foot thick and 5' away from you it's paper thin because of the stream of 50 something degree ground water coming up from 20' down. Some places you can see it swirling the water in the holes. In summer, swimming along in 80-85 degree water you can feel the 50 degree ground water blasting up. Gives you the shrinks. :laughing:
And the springs move around a lot. Sometimes they come out of the bank right at the water's edge. One winter it was about 0F, snow cover everywhere on January 1st, and right where the high bank meets the water, there's about 1 foot of mud about a hundred feet long and 50 robins pecking away. That's the earliest I've ever seen robins around here.
Anyhow, best to drill a lot of test holes. A lot of guys carry a heavy spud bar and whack the ice three times in front of them as then go along. If the spud bar pokes through, turn around and go back.
I carry a whistle and ice picks around my neck at all times when on the ice. I'm thinking about getting an ice fishing jacket. They keep you warm, and they float! Makes it much easier to self rescue.