Been a while since I've posted (been busy with all kinds of things).
I'd like to add my two cents to the discussion.
I've "sailed" (OK, we motored as sailing wasn't an option) from Portsmouth, RI, to Annapolis, MD, in May of last year. It was very, very cold, very, very windy, and a bit wet (we were blessed not to get rained on).
Here's what I wore:
Undershirt. Can be anything, cotton, whatever. In this case it's the layer you want to add the air pocket you need.
Silk undershirt. Longsleeve. A MUST.
Silk longjohns. A MUST.
Thermal skiing tights. I have a pair from my cross-country days (not too many of them unfortunately). I skiied once when the windchill brought temps down to -20. I had no idea it was that cold (wasn't cold and didn't feel it, but the wind was definitely ripping). 'Twas up in Minnesota.
Heavy jeans. Helps keep the wind out actually.
Turtleneck. Heavy weight is better. The neck helps to retain body heat.
Fisherman's oiled wool sweater. Really heavy, stretchy, with good loft. Mine is an old Land's End sweater (maybe about 15 years old?). I can usually wear just that over a turtleneck, silk undershirt, t-shirt and be quite toasty - no jacket needed. Although on the water I DID need the jacket.
Synthetic skull/watch cap. EMS had a nice spandexy thing that really kept my head warm.
Fleece cap. Wore that over the watch cap. No problems with heat loss at all.
SLAM foul weather bib overall. Breathable PVC. Worked GREAT! A little tough to get out of with layers on, but, with practice it got easier.
SLAM jacket to match. Not great for heat retention, but did add a layer. 'sides, it matched.
NorthFace Summit Series Mountain Parka/Climbing Jacket. That jacket is awesome! Warm, dry, waterproof, windproof, and lightweight. Great hood too! Held up under salt water spray pretty darn well to boot.
SmartWool socks. Can't beat 'em.
Waterproof, insulated, hiking boots. Perhpas a no-no as far as deck cleaning goes, BUT, in cold/wet, you can't beat 'em! Mine didn't leave any marks and I was glad I took them! EMS top o the line brand too.
Eddie Bauer thinsulate gloves. I used these as a liner.
West Marine cold-weather sailing gloves. Windproof and waterproof, with cuffs. Light on the insulation (hence the use of the other gloves above). Once lined the combination kept my hands from freezing.
One thing to bear in mind on a boat is that you do more sitting than moving in most cases. So, you have to dress a little heavier than if you were constantly moving. By varying the layers you can accomodate much by way of temps/conditions.
Also, go with wool or silk as either will still keep you warm when wet. Cotton won't do squat for you that way (although as an undershirt coupled with the silk it works out just fine). Fleece also keeps you warm when wet. Though fleece can easily cause you to become overheated. Watch the artificials as they may not function as advertised - such has been my experience as an outdoorsman of sorts.
The best advice is to dress such that you either don't sweat or keep that to a minimum. Lots of sweat is your enemy as that will eventually chill you.
Having used both breatheable PVC and GoreTex, I can recommend both. I like my SLAM gear - it isn't the offshore rig they sell, but it worked really well on top of the proper layers. I appreciated greatly my NorthFace jacket. I've bought NorthFace most of my adult life and don't intend to switch (despite their seemingly really high prices) as the garments hold up really well under the harsh treatments I give 'em.
In cold winds, wrap something around your neck such as a scarf - you'll appreciate that!
Well, that's enough - my 3 year old's behind needs to be changed (he refuses to train up at this point).
Peace, Love, and Light,
/s/ Jon C. Munson II
P.S. I don't know if these are made any more, but there used to be a two-layer "longjohn" system of cotton on the underside and wool on the outer. I used that when installing security alarms and that stuff kept me quite toasty! So I'd recommend that as well.