I have a theory about why salt water works. Osmosis. When you sit in a bathtub for a long time, you resemble a prune because the water outside your skin is less diluted with other stuff than the water inside your skin. It passes through your skin until the ratio of water to stuff is equalized. (at which time you would look like a zeppelin and probably not be breathing.)

If you soak a body part in salt water, it has the reverse effect of pulling water out of the tissue. In effect, you're drying out the skin you soak in it, killing and forming a layer of dead skin cells.

And now, answers to possible questions:
1) No, I'm just guessing - does someone know for sure?
2) I don't know Catspaw, why don't you try it and tell us what happens.