A sliding device for sliding on the ground down a sloped or inclined surface (grass, dirt, sand, synthetic turf, etc.) has an upper deck and a slide mechanism mounted below and in parallel with the upper deck. The slide mechanism has a slide base formed by upper and lower planar members spaced apart and extending horizontally in parallel, with an enclosure formed by left and right braces and front and rear braces with radiused ends, and an endless anti-friction belt is entrained to slide around the slide base. The slide base is formed as an air tight enclosure provided with a portable air pump mechanism, and the lower planar member has an array of small air holes to let pumped air out to form an air layer between the lower planar member and the belt sliding around it for reducing friction and higher downhill sliding speeds. The device may be used for sliding down a hill like a body board, boogie board, surfboard, sled, ski, or skateboard.