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****When I was a teenager, I cracked through the surface of an Ohio strip-mine pond during a December pheasant hunt and couldn’t hoist myself back onto the ice. My friend Bill Morris extended his Stevens side-by-side to pull me out, to date the only time I’ve felt good about looking down the barrels of a shotgun.

Ice safety has been no small concern to me ever since, especially considering that I now live in Montana, where you don’t have to go ice fishing to find your progress regularly interrupted by ice. Here’s what you need to know about the hard water.

Strong Impression
Ice is generally said to be thick enough for walking and fishing at 4 inches. But not all ice is created equal. Clear ice that forms in December will be stronger and more elastic than the same depth of ice in March, when the bonds fusing the crystals have become stressed from spring sunlight, giving it a honeycombed appearance. Color also counts. Beware of black, gray, or milky ice, which lacks the strength of clear green or blue ice. Expect snowpack or standing water to weaken ice, and steer clear of exposed rocks and logs, which can conduct heat to the surrounding ice. Decaying vegetation also leads to unstable conditions.

Seldom is ice uniformly distributed across a lake surface. Ice near shore, which is subject to both conductive heat from the land and reflected sunlight from the bottom, will be weaker than ice that forms over open water. Springs and inlets can prevent the formation of safe ice. Even waterfowl and schooling fish, such as carp, can slow ice formation by circulating the water.

Touch and Go
The golden rule of walking on ice is “Probe as you go.” Use an ice chisel or spud bar with a sharpened point to act as your “ear to the ground”: Safe ice sounds solid and dull when you thump it. Rotting ice creaks or feels spongy. A single hard jab will usually break through ice less than 3 inches thick. Thickness can be approximated by studying the dry cracks that radiate through the ice (not to be confused with elevated pressure ridges, which you should strictly avoid).

If in doubt, test ice thickness with an auger or, more efficiently, a cordless, 1/4-inch drill with a 5/8-inch wood auger bit. Carry a retractable tape measure for a precise measurement.

Crawl, Don’t Walk
The most important self-rescue tool for your ice-fishing jacket is a pair of ice picks. They are easily made by pounding nails into the ends of two 6-inch sections of wooden dowel (cut off the nail heads, sharpen the ends, and cover with corks when carrying). If you do fall through, turn around, face the ice you just crossed, and use the picks to claw yourself on top. Distribute your weight as widely as possible by rolling and crawling to thicker ice. If your companion falls through, toss him an empty Clorox bottle or a piece of wood tied to a 50-foot rope. Rope should be a standard part of your ice-fishing kit, but if you don’t have any, try dragging a dead tree or very long branch from the shore, lying down to distribute your weight, and pushing it toward the victim. But if you approach too closely, you’re running a grave risk of turning one man’s potential tragedy into the certain death of two. It’s safer to call 9-1-1 and hope help arrives in time.