An underwater breathing aid is a device used to allow a person to breathe while submerged in water. The two most common types of underwater breathing aids are SCUBA (Self-Contained Underwater Breathing Apparatus) and SNORKEL (Submersible Nose and Oral Respiratory Kit with Elastic Lanyard). SCUBA is a full-face mask that covers the entire face and provides air from a tank, while SNORKEL is a tube that extends above the surface of the water and allows the user to breathe without having to come up for air.