Alcoholic beverages and hydration/dehydration

I understand that if I were stranded in the desert, a bottle of rum would not only fail to do me any good, it would hasten my demise. However, what about beer? At what proof do alcoholic beverages become useless for hydration?

I cannot speak to beer, but if I don’t drink enough water along with my Mike’s Hard Whatevers (especially, if I have more than two in rapid succession) I get leg cramps - the painful kind that hit the upper inner thigh. And I have heard similar from friends. It, based on the resulting cramps, depletes the natural potassium in your body.

Here is a thread I started asking a similar question a while back ago.