Nope, I'm not doing it! Nosirree!
I just came across an online brochure published by a local club, the Chesapeake Paddlers Association. It addresses the dangers inherent in the body's responses to immersion in cold water. One part that caught my eye said:
"Exposure of the head and chest to cold water causes sudden increases in heart rate and blood pressure, which may result in cardiac arrest. Uncontrolled rapid breathing (hyperventilation) follows the initial gasping response and may also lead to unconsciousness. The victim must attempt to recover a normal breathing rhythm as rapidly as possible."
Hey, I've experienced that even while swimming in a nice warm wetsuit when starting out in cold water!!
It also states: "Strong swimmers, without thermal protection, have died before swimming 100 yards in cold water."
Yikes! I suppose my decision not to do any more ocean-swim events in cold water without a wetsuit makes perfect sense after all!