It's called the "reflexive torso gasp" and it's responsible for more late-season recreational boating fatalities than hypothermia. With that in mind, the Pennsylvania Fish and Game Commission is urging anglers, hunters and recreational boaters who frequent late-season waters to wear life jackets.

Cold water shock is caused by sudden immersion into water cooler than 70 degrees (water temperatures are now falling into the 50 degree range). Sudden immersion triggers an involuntary reflexive torso gasp, causing the victim to inhale water, become disoriented, panic and lose the physical ability to swim.

"It is very common for even strong swimmers to go under very quickly in cold water," said Boating and Access Director Dan Martin. "They don't have time to get hypothermia ... they drown too quickly for hypothermia to be a factor."

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