Jerry,
While I think you and I mostly agree on the general aspects of cold water immersion, I have to take issue with a few specific points you made. I have highlighted in bold the specific points I want to address.
It has been looked into extensively. Mostly at the University of Victoria in British Columbia. The most complete testing on human subjects was done in the '70s and led to: Hayward, J.S., Lisson, P.A., Collis, N.L., and Eckerson, J.D. Survival Suits for Accidental Immersion in Cold Water: Design-Concept and their Thermal Protective Performance. Dept. of Biology. Univ. of Victoria, B.C. 1978. I have not found a copy online and don't know if I can find my copy, but testing was done in Victoria Harbor on students wearing several different types of clothing. As you might expect wool was better than cotton (but not as much as you might expect) and the fit of the clothing made a difference but again the activity was more important (see below). Human testing of this sort will probably never be done again, but it was a sea change in our understanding of immersion hypothermia.
There has in fact been a great deal of human testing done since the '70s. In particular,
Gordon Geisbrecht (AKA "Prof Popsicle") at Univ of Manitoba has done many experiments, both on himself and students. One difference from the older work at UBC is that by using modern electronics, Geisbrecht and others can now monitor core temperature in real time. For a list of some of Geisbrechts many publications
go here. For graphic views of some of his human subject testing, see
Cold Water Bootcamp (Canadian version], and
Cold Water Bootcamp USA. I highly recommend getting a copy of the "Beyond Cold Water Bootcamp" DVD. It has some remarkable footage of circum-rescue collapse.
This work led Hayward to develop what is now the Mustang ThermoSystem Float Coat. The beavertail (or diaper at is commonly called) changes a moderate increase in survival time to a huge one (the modern coat is even better than the original). I have used one for many years and would not be comfortable offshore in cold water without it. I have had it in the water many times (for practice, my only sinking ship I got off with dry feet). Mustang makes several other coats so fit of one may not control fit in the ThermoSystem.
The following is a bit of information from this work that was printed in a pamphlet by Hayward through the Sea Grant Program at UBC. ir.library.oregonstate.edu/xmlui/handle/1957/24392?show=full
SUMMARY
The following table summarizes how a selection of
different situations can affect predicted survival time
of the average adult* in water of 50OF (100C):
I presume this is a typo and you meant 50 F and 10 C? (500F is about the temperature that paper burns, and 100 C is the boiling point of water.)
Situation Predicted Survival Time (Hours)
NO FLOTATION
Drownproofing 1.5
Treading Water 2.0
WITH FLOTATION
Swimming 2.0
Holding-still 2.7
H.E.L.P. 4.0
Huddle 4.0
UVic Thermofloat 9.5
*Clothing worn was cotton shirt, pants, and socks, plus
running shoes.
This seems to imply that a PFD makes no difference, and you can survive about 2 hours with or without a life jacket?
Geisbrecht's work has made it abundantly clear that a PFD makes a huge difference. Without a PFD, cooling of the limbs makes it difficult or impossible to swim long before your core cools to even mild hypothermia. Without a PFD in cold water you can't swim long enough to become hypothermic, instead you drown first.
I totally agree that a float coat is a great idea if one is around cold water. Floatation coverals (a work suit) is even better. A full-on insulated dry survival suit (a "gumby suit") is best of all.
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