"666" wrote...
can you recommend any products designed specifically for high-seas sailing?

In general, stay away from down, which is fairly useless when wet. Look for
bags stuffed with Dupont "hollofill" or "quallofill" (or similar). The stuffing
fibers are made from miniscule tubes that retain their insulating properties
even when wet. You may need to get a separate waterproof cover, or use
Scotchguard or similar waterproofing on the sleeping bag outside cover.