Abstract: A sliding assembly with a simple structure for smooth water-lubricated sliding includes first and second sliding elements each having a sliding surface. The sliding surfaces come in contact with each other with a water layer in between to allow the first and second sliding elements to slide relative to each other. Each of the first and second sliding elements includes a base member and a hard layer as the sliding surface on a surface of the base member. The hard layers in the first and second sliding elements include nanosilica layers supporting nanosilica particles. The nanosilica layers each have a surface covered with the water layer, allowing water-lubricated sliding with an appropriate sliding velocity under an appropriate load. The first and second sliding elements slide relative to each other with low friction.