With the walleye and northern fishing season opening on May 14, the Minnesota Department of Natural Resources (DNR) reminds anglers that even on a warm day in the boat, water temperatures can hover in the low 50s.
A 2007 report by the U.S. Coast Guard stated that a boating accident is five times more likely to be fatal if the water is colder than 60 degrees.
“Cold water can kill in ways that you might not expect,” said Tim Smalley, DNR boating safety specialist. “Nearly everyone knows that immersion in cold water can cause hypothermia – the abnormal lowering of the body’s core temperature. What most don’t know is that cold water immersion has several stages, any one of which can cause death.”
Victims who experience an unexpected fall overboard suffer initial cold water shock in the first minute, which involuntarily causes them to take a series of big breaths, called hyperventilation. If a person’s head is underwater, they can inhale more than a quart of water and drown immediately.
Those who keep their head above water will continue hyperventilating as their blood pressure jumps, Smalley explained. If they can’t control their breathing within 60 seconds, they’ll suffer numbness, muscle weakness or even fainting, which leads to drowning. A person with heart disease may experience sudden death due to cardiac arrest.
A victim who survives the first minute of cold shock and hyperventilation will progress to the second stage called “cold incapacitation,” or swimming failure. Within about 10 minutes, rapid cooling of the extremities causes muscle stiffening so a person will no longer be able to perform the tasks, such as swimming, holding onto a floating object, or putting on a life jacket. Even yelling for help can be difficult.
Hypothermia is the third stage. Smalley said there is a common misperception that it sets in almost immediately after a person lands in cold water. However, a victim won’t start to become hypothermic for 30 minutes. Severe hypothermia can take an hour or more to set in, depending on the water temperature, body mass, clothing, the amount of struggling and several other factors. A body core temperature of 95 degrees is considered hypothermic, loss of consciousness occurs at about 86 degrees, and death is imminent when the core temperature drops below 82. Unless a person is wearing a life jacket, drowning will occur long before severe hypothermia gets them.
Most boating fatalities are the result of capsizing or falls overboard, not collisions between boats running at high speed. “We see it time and time again in Minnesota boating accidents,” Smalley said. “A single boat on a lake capsizes, the victim isn’t wearing a life jacket, has no warning or time to put one on, and drowns due to the effects of cold water.”
Experts recommend that people who end up in the water stay with the boat, even if they aren’t able to get back in. They are more likely to be seen by potential rescuers if they are next to a boat. A person should only swim for shore if wearing a life jacket, if the likelihood of rescue is low, or they are close to shore and aren’t able to climb back into or on top of the boat.
The key is the life jacket, Smalley said. A person who suffers swimming failure or loss of consciousness will stay afloat wearing a life jacket, but drown without one.
Smalley said smart anglers wear a life vest from the time they enter the boat until they return to shore. “There is no time to put one on before a boating accident,” Smalley noted. “It would be like trying to buckle your seat belt before an imminent car crash.”
As of May 9, there had been no 2011 boating fatalities in Minnesota. Last year at this time, there had been one death on Lake of the Woods, where a woman who was not wearing a life jacket fell from her boat and drowned.