The poion of the skin that serves as a barrier to water loss is the:

The keratinized epidermis, which is the most superficial layer of skin, is responsible for serving as a barrier to water loss. The dermis, found directly below the epidermis, contains collagen and elastin, fibers which provide the skin with tensile strength and tone. The dermis also contains hair follicles, sweat glands, and sebaceous glands. The subcutaneous tissue (hypodermis, superficial fascia) is a loose and fatty connective tissue. It protects the skin from bony protuberances and helps with thermal regulation. The subcutaneous tissue also contains sweat glands and cutaneous nerves. The deep fascia is a dense layer of connective tissue that invests structures such as the muscles.