For walking, I would suggest Sorel boots, particularly the Glacier http://www.sorelonline.com/html/products/pagem8.html These boots are designed for everyday wear in harsh conditions. The Glacier model is supposedly warm down to about -40'c. I have the Caribou II, a slightly lighter style, which has proved itself to be warm down to to -20'c this Xmas. I don't know how waterproof these are in practice, but I would imagine that any water remaining unfrozen in a typical Alaskan November may be too fast-moving or tidal to be safely crossed on foot anyway.
Sorel have recently been taken over by Columbia, so you can currently find their boots discounted to under $100 on many US and Scandi websites. They are hard to find in the UK, though I've seen them at Lang and Hunter in Kingston in the past.
They are generously sized for wearing with multiple socks. Fit is more wellie-like than boot-like, which slows you down slightly, but has the advantage that you can wiggle your toes to keep warm.