Cordwainer, I would suggest that keeping warm is literally a matter of life and death for many sports and pursuits, and that the doc who said "give up sailing" needs to get his head out of his, ahem.
Anyone who pursues winter sports can tell you that hypothermia and frostbite can kill. And, how to avoid them by eating properly, dressing properly, etc.
A wool watch cat to keep the head warm and preserve body heat. Wool or silk undercloths to keep the core warm and dry, and allow heat to get out to the limbs. And here in the US, Graber? Grabber? brand heat packs, which generate heat when exposed to air. They make a wide range now, including packs that slip into your gloves and boots, packs that stick to your clothes, great way to supplement body heat when you need it. Then there are also electric socks and gloves and vests, often sold to the snow ski and motorcycling markets.
Give up sailing? Hell no, just sail warm and dry. That's easily possible.