Quote Originally Posted by littleleemur View Post
The heat packs are the gel ones where you flex a metal disc that is floating around inside when you use it the first time. It hardens and becomes opaque after the first use and you'll have to boil it until all of it is clear to re-use it. 2 types are generally available, with & without the metal disk. Those without can be reheated v. carefully in the microwave.

http://www.roshgo.com/Merchant2/merc...c01/CTGY/00602

Some sort of fanny pack/vest with strategically placed pockets is usually used to prevent burns as you can't adjust underwater.

As for the instant ones, the problem is how the chemicals react with each other under pressure.
That be the critters, although the ones I saw close up appeared to be encased in some sort of vinyl covering. I cannot seem to recall if they were wearing light garments under their suits or what, I just know they were avoiding direct contact with their skin by having a barrier in place with the heat packs riding comfortable between the barrier and the inside of the suit. These guys do tend to get cold on ling dives, so to hear them report staying warm through deco (motionless, the ideal time for cold to set in) said a lot about the products they were using. I'll get in touch with them to see if they still have a copy of what they posted a few years back as well as any possible updates (I do know that both Gary and Moonfuzzy still dive wet.)