Greenwell, so you think the fur on the hare's foot is waterproof, not water resistant? Meaning, impervious to water absorption?
Yes, the stuff absorbs very little, if any, water. Otherwise the rabbits would have wet, cold feet. My friend Galen Mercer still uses snowshoe foot fur as an aid to flotation in his flies and what is most interesting about this is that he never uses floatant of any kind, believing that it may alarm the trout with it's odor and so forth.
One thing about foot fur is that it is fairly dense (solid)and heavy for a fur or hair and doesn't have the buoyancy that some materials do; it floats lower than things like CDC. This can be mistaken for poor flotation properties but it's actually not. Approach it as a material for flies that you want to float low in the surface film.
Like I said earlier, one can give a fly tied with snowshoe hair a "pop" with a false cast and it will float like it just came from the fly box. Also, it doesn't absorb fish slime so a quick rinse in the river, a squeeze with Amadou, a false cast and you're back in business. We used to fish a lot in the late evenings and right through until dark and often used Usuals for just this reason, besides the fact that they are great catchers. All this nostalgia makes me want to tie a few and fish them again!