Basic Ice Do's & Don'ts:
DO remember that ice is truly NEVER 100% safe. No matter what its measured thickness is, riding on ice always comes with some risk.
DON'T venture out on the ice until there is at least 4 inches of clear, solid ice. Thinner ice can support one person, but since ice thickness can vary considerably, especially at the beginning and end of the season, 4 inches will provide some margin of safety. There are many factors that can change ice thickness coverage and create varying measurements. Warm water from the bottom of the lake, stream or pond can flow to the surface in areas where fish gather, or become weak from the warmth that a gathering flock of waterfowl creates.
DO go out with a friend and keep a good distance apart as you walk out. The reasons are two-fold: 1) If one of you goes in the other can call for help (just about everyone carries a mobile phone nowadays). 2) Your companion can also attempt a rescue if one of you are carrying rope or other survival gear.
DON'T measure ice thickness in one spot only. You need to take multiple readings in completely different areas to get a good feel for the actual ice depth. Again, ice thickness can vary greatly from one spot to another.
DON'T park vehicles, trailers, or sleds right next to each other when on ice. This will place undue stress on one small portion of the ice increasing the chance of ice fracture. Spread them out.
DO carry a long length of rope when riding on ice. This may be a victim's only chance of getting pulled out from the water and to safety.
White and crispy, just too risky. Clear and blue, it's better for you.
That's the old saying and it's a good one. Take a real hard look at the ice before you venture on. Clear blue ice is the strongest, and it still takes three inches to safely hold a single person, and five to six inches to safely hold a group of people or a single snowmobile.
Ice is very inconsistent. Milky, honeycombed ice that has air bubbles or snow crystals trapped in it is much weaker and less trustworthy than clear blue ice. Water currents under the ice or springs can create weaker spots that will hold up people but not anything heavier. In other words, varying ice thickness can and will create weak spots, which can lead to ice fracture. Know before you go!
Snow cover can complicate things with ice. Not only does it keep you from visually checking the ice for inconsistencies, it also insulates and inhibits ice formation. So be extra careful before venturing out onto a snow covered pond or lake.
The only way for sure to tell how thick ice is, of course, is to cut a hole in it with a chisel or auger. Start near the shore and make several test cuts as you go out. Remember that ice thickness isn't consistent. Water currents (particularly around narrow spots, bridges, inlets and outlets) are always suspect. Never trust the ice on a river or stream -- it can be several feet thick in one place, and unsafe only a short distance away.
On really cold days, you are likely to hear the ice rumbling and pinging, almost sounding as if it is cracking. Sometimes you'll even see long cracks developing. Don't panic. As long as you KNOW FOR SURE that the ice depth is within safe limits, it's really nothing to worry about. Those rumblings and cracklings are the sound of pressure being relieved as more ice forms beneath the surface. The ice is actually getting safer!
WHEN THINGS REALLY GO WRONG:
If you fall through the ice, here's what you need to know!
You need to devote all your efforts and power to get out of the water immediately. While this may sound silly, people do sometimes worry about material items at first, like the sled that just went under. You need to act quickly though, before you lose full use of your hands and limbs. Forget trying to get the tow strap on the sled and climb onto anything floating.
In frozen waters, you'll have only about 20 minutes before you will lose consciousness. You can extend this time greatly by keeping calm, keeping your head and neck out of the water, and by moving only if necessary to escape. If you ABSOLUTELY KNOW you CAN'T get out, keep still until help arrives. This will conserve your body heat.
If you are alone and think you can get out, place your hands and arms up on the ice while violently kicking your legs in an attempt to push yourself out of the water and up on the ice. If you do indeed get out, DO NOT STAND UP! Gently push yourself while remaining flat until you get a safe distance away. The fact that the ice gave way in the first place should automatically tell you that the area you are near is not stable. Get as far away from the fracture as possible before attempting to stand.
If you are UNABLE to get out, you should immediately stop moving and go into "Heat Escape Lessening Position" (H.E.L.P). Hold your knees up to your chest to protect the trunk of your body from heat loss. Wrap your arms around your legs and clasp your hands together. Keep your neck and head out of the water. Remain as still as possible, however painful. Intense shivering and shaking are natural body reflexes in cold water but cause rapid core heat loss which will speed hypothermia.
Do not attempt to swim UNLESS it is to reach a nearby shore, boat, another person, or a floating object on which you can climb or lean. Unnecessary swimming "pumps" out warmed water between your body and your clothing circulating new cold water to take its place. Unnecessary movement of your arms and legs pumps warm blood to your extremities, where it cools quickly, reducing your survival time by as much as 50%!
If you are in the water, unable to get out and awaiting help, DO NOT REMOVE CLOTHING, despite what you may have been told. Instead, button, buckle, zip and tighten collars, cuffs, shoes and hoods. Cover your head if possible. A layer of water trapped inside your clothing will be slightly warmed by your body and help insulate you from the colder water, slowing your rate of body heat loss.
FIRST AID FOR HYPOTHERMIA:
Any person pulled from cold water should be treated immediately, by medical professionals, for hypothermia.
Symptoms of hypothermia include intense shivering, loss of coordination, mental confusion, cold & blue (cyanotic) skin (especially around lips or fingers), weak pulse, irregular heartbeat and enlarged pupils. Once shivering stops, core body temperature begins to drop critically.
Your goal in treating hypothermia is to prevent further body cooling. Severe cases call for rewarming by trained medical personnel. In all cases, arrange to have the victim transported to a medical facility immediately.
What To Do:
Gently move the victim to warm shelter. Check breathing and heartbeat. In cases of hypothermia you should monitor victim very closely. Start CPR if necessary. Remove victim's clothing with a minimum of movement, cut them away if necessary. Lay victim in a level face up position with a blanket or other insulation beneath them. Wrap victim in warm blankets, sleeping bag or other warm covering.
If there will be a long delay before victim arrives at a medical facility use the following rewarming techniques:
Apply heating pads or hot water bottles (wrapped in a towel to prevent burns) to the head, neck, chest and groin. DO NOT apply heat to arms and legs or give the victim a hot bath. This forces blood out through the cold extremities and back to the heart, lungs and brain which will further drop the core temperature. This can cause "after drop" which can be fatal. Do not massage or rub the victim, rough handling may cause cardiac arrest. Apply warmth by direct body to body contact. Have someone remove their own clothes and lay next to victim skin to skin. Wrap both in blankets. If person is alert enough you can give them hot drinks. If they are unconscious or stuporous do not give them anything to drink. Never give alcoholic beverages.
EXTREMELY IMPORTANT!
ALL HYPOTHERMIA VICTIMS MUST BE TRANSPORTED TO A MEDICAL FACILITY IMMEDIATELY, EVEN IF THEY APPEAR TO BE OK. "AFTER DROP" AND CARDIAC PROBLEMS ARE KNOWN TO HAPPEN DURING THE RE-WARMING PROCESS AND ARE LIFE THREATENING, EVEN IF THE VICTIM SEEMS TO BE RECOVERING WITHOUT PROBLEMS!!!
SIDE NOTE: COLD WATER DROWNINGS
Some apparent cold water drowning victims may look dead, but may actually still be alive! A phenomenon called the "mammalian diving reflex" can be triggered by cold water. This reflex, common to whales, porpoises and seals shuts off blood circulation to most parts of the body except the heart, lungs and brain and slows the metabolic rate. What little oxygen remains in the blood is circulated where it is needed most.
Do not assume that a person who is cyanotic and who has no detectable pulse or breathing is dead. ALWAYS administer CPR and transport the victim to a medical facility immediately for specialized rewarming and revival techniques. Most frozen waters are cold enough to trigger this reflex. People have been revived after having been submerged for extended periods, some in excess of 45 minutes!
So don't give up.
UPDATE:
Please take a few minutes to view a "Falling Through Ice" video created by The Discovery Channel. It is a very good video providing important information.