What happens if you stay in salt water too long?

Depends on your definition of "too long". First, your skin will dry out. Second, the salt will start to work its way into your tissue. Third, it will burn. Fourth, the salt will dry your skin tissue to the point of rot. Eventually, you will experience what only cadavers and catatonics experience. Skin-slip. You will go to finally get out after several days and the tissue on your arms, legs, belly and back will randomly slip out of position.