The word SCUB refers to the apparatus used in diving that provides the diver with a continuous supply of compressed air. There are several other terms used to describe similar apparatus, including rebreather, oxygen rebreather, and underwater breathing apparatus. A rebreather is a device that recirculates air into the system, while an oxygen rebreather uses pure oxygen to supply the diver with breathing gas. Underwater breathing apparatus encompasses a range of devices including SCUBA gear, hookah diving systems that supply air from the surface through a hose, and closed-circuit rebreathers that recycle exhaled air. Whatever the terminology, these tools have revolutionized underwater exploration and allowed scientists, divers, and adventurers to explore the depths of the oceans with ease.