Abstract: A device for use in activity on snow-covered surfaces, water or also on another surface, comprises a bottom board (1) for contact with the surface, equipped with longitudinal steering ribs on the underside and with upwardly curved faces at the front edge and preferably also at the rear edge, and a top board (2) that is adapted to the user and his position of use by the formation of well-like depressions along the side areas for the user's legs and having an air bag (3) for support of the user. The bottom board (1) and the top board (2) are joined together along their edges and define a hollow space between them. An airtight bag (3) that projects above the top board (2) is located in the central area of the device. The bottom board (1) has a longitudinally flat or slightly concavely curved central portion (10) which extends from the curved front portion to the rear portion of the board, and with side faces (11) on each side that are higher than the central portion and the surface for the board.