Skin permeability may change seasonally in snakes to help with the problem of drying out. It is known that desert snakes have generally impermeable skins, and that aquatic snakes have a more permeable skin that can sometimes trap water to prevent drying out. Some snakes may change their environment throughout the year, and may subsequently change their skin's permeability as a result. For instance, aquatic snakes may latch on to more water if they are in an environment that is drying out by attracting a layer of water under their scales.