Paradoxical undressing, sounds like my college days...
http://www.coldwaterbootcamp.com/pages/preventionv2.html
There is a cool chart on the link that describes the various stages of hypothermia. I think if you're getting to the point of wanting to get naked, you're pretty far along. Above 95 and you're just cold challenged, 95-90 is mild hypothermia but recoverable with some help. Below 90 and you're going to require outside medical assistance, and important to note that people below 90 need to be handled in a way as to not jostle them, or you can increase the chance of cardiac arrest. I was told in a WFR training medics/hospitals can hook you up to a machine intravenously, which gradually warms your blood and body temperature, reducing the chances of cardiac arrest as cold blood begins to re-circulate throughout your system. The ability to properly get someone into a hypo-wrap and having the materials on hand is a good skill to have if venturing out in cold conditions. Always good to paddle in a group, but even more so in cold conditions, a cold challenged/hypothermic person can require a lot of assistance.