I'm not an expert (never tried the 12mm or thicker hoods), but you might consider wearing an eighth-inch thick neoprene "ice cap" underhood along with whatever 7mm hood goes well with your drysuit.
Combined with my 7mm DUI hood, I find it very effective down to the low-30's. I don't expect to get into colder water very often.
I use Henderson, but several other companies make them.
http://www.scuba.com/scuba-gear-28/022135/HENDERSON-ICE-CAP.html
It has a smooth surface that seals very well around the face and covers most of it, leaving only the lips themselves exposed. The lips don't get cold easily because they are so well vascularized.
With a regular hood, it's usually the tissue near the lips that gets cold first, but that's enough to reduce circulation to the lips themselves, allowing them to get numbingly cold. That just doesn't happen with the ice cap covering those adjacent tissues. I was amazed!
Also, the mask skirt seals on top of the underhood, then the smooth surface of my DUI hood seals on the top edge of the skirt and on the underhood around the face.
I have finished long dives and found most of the underhood still dry when I took it off! :11:
You may find it quite versatile in that you can go without the ice cap when the water gets up to your comfort zone. I wear mine in water as warm as 60 degrees, then go with just the 7mm.
It's probably a little more trouble to don two hoods instead of one thicker hood, like a single 12mm, but it's worth it to me to have such a great seal and almost complete coverage of the face.
Dave C
Combined with my 7mm DUI hood, I find it very effective down to the low-30's. I don't expect to get into colder water very often.
I use Henderson, but several other companies make them.
http://www.scuba.com/scuba-gear-28/022135/HENDERSON-ICE-CAP.html
It has a smooth surface that seals very well around the face and covers most of it, leaving only the lips themselves exposed. The lips don't get cold easily because they are so well vascularized.
With a regular hood, it's usually the tissue near the lips that gets cold first, but that's enough to reduce circulation to the lips themselves, allowing them to get numbingly cold. That just doesn't happen with the ice cap covering those adjacent tissues. I was amazed!
Also, the mask skirt seals on top of the underhood, then the smooth surface of my DUI hood seals on the top edge of the skirt and on the underhood around the face.
I have finished long dives and found most of the underhood still dry when I took it off! :11:
You may find it quite versatile in that you can go without the ice cap when the water gets up to your comfort zone. I wear mine in water as warm as 60 degrees, then go with just the 7mm.
It's probably a little more trouble to don two hoods instead of one thicker hood, like a single 12mm, but it's worth it to me to have such a great seal and almost complete coverage of the face.
Dave C
