RAW coconut oil!! Hydrogenated oil will kill you eventually so make sure its RAW. .(I usually have a bowl of Oatmeal with honey, raw coconut oil and sometimes Ghee about 45 minutes before a winter dive - also drink plenty of water. I usually bring along a mixture of lime juice, water and honey.)
I've been diving several times a week all winter for a couple of years - water - temp 1 or 2c - air quite a bit colder, wind, blizzards, waves etc. etc. As Connor mentioned I mostly have used a 6 mil smoothskin out top and 5 mil bottoms with superstretch nylon out - not farmer johns. I had elios make me a 1.5 mil titanium lined vest which I can use under any of my suits - it does help reduce any water circulation and does not restrict breathing like a farmer john.
My suits are black shadow neoprene with the new black coating inside. I don't think it really makes much difference though in terms of putting on and taking off. I have a plain open cell suit and I think its actually easier.
Last year I used a 5 mil smoothskin out suit with the 1.5 vest under it and was fine all winter. Before I got my 6 mil I used a 5 mil open cell/superstretch nylon out suit all winter and was fine too - just not for quite as long. I generally go for anywhere from 90 minutes to 3 hours. A henderson ice mask will do a lot to help you stay warm if you don't mind being insulated from the environment. I used to use one but quit a couple of years ago. My dive buddy uses one and its really embarrassing.
I use a monofin for all my diving and in the winter I do fin sprints whenever I get cold - and generally have a more active style of diving because long, stationary breath holds will get you very cold very fast.
In really cold weather I drive to the site with my suit on rather than expose myself to the cold before diving . If you get a chill before diving you'll never recover. These suits are easy to put on and take off if you use enough lube - the only linings that make a difference are fabric and they greatly reduce the thermal efficiency of the suit. In air the combination of the suit with a good windbreaker and wind pants is very warm.
My suggestion is 5 or 6 mil open cell bottoms (not farmer john) with nylon out and a 5 or 6 mil open cell top with smoothskin out combined with a 1.5 mil vest (mine is titanium in/nylon out). Get a freediving suit - forget about zippers. You've got to be careful with the smoothskin out top - use plenty of lube.
Jon is actually the one who turned me on to this whole winter freediving thing. He talked me into a 6 mil instead of a 7 - now I mostly use a 5
I discovered the importance of smoothskin on the outside diving with Eric F, Pete S. and Tyler Z in BC - they were all way warmer than me in their smoothskin suits (I used a 5 mil superstretch out). The heat wicking in air is really significant.
In the first video on my site the water temp is approximately 3C and I am wearing a 5 mil open/smooth suit.
