Abstract: An impeller includes a hub, and a vain unit provided radially at a position spaced apart by a predetermined distance based on the hub. The vane unit is configured to begin at a position spaced apart by a predetermined radius based on the hub and to end to be formed into a streamlined shape in which a beginning portion becomes narrower in width than an end portion. The vane unit includes “n” first vanes radially configured at positions spaced apart by a radius r1 based on the hub and having a first length, where “n” is a natural number equal to or greater than 3; and “n” second vanes disposed between the first vanes, the second vanes having a second length that is less than the first length of the first vanes.

Abstract: Disclosed is an underwater camera, including: a casing having an accommodation space for a camera module; a connector coupled to a first side of the casing and transferring a signal output from the camera module to a controller; a lens connected to the lens and coupled to a second side of the casing in a manner that a periphery portion of the lens is embedded in the second side of the casing; a sealing means coupled to the second side of the casing and preventing water from entering into the casing and from reaching the lens; and a valve coupled to the first side of the casing and having a hose connected to a sealed space provided between the sealing means and a surface of the second side of the casing, thereby discharging air from the sealed space and supplying an inert gas into the sealed space.