A water-resistant watch case of a diving watch, includes at least one back mounted on a lower side of a middle part, and a crystal mounted on an upper side of the middle part. The crystal includes an annular peripheral surface to be fastened with an amorphous metal gasket on an inner annular surface that is complementary in shape, on the upper side of the middle part. The annular peripheral surface of the crystal is inclined towards the inside of the watch case at a determined angle less than 90° relative to a central axis perpendicular to a plane of the watch case to distribute stresses between the crystal and the middle part due to the water pressure during a dive. The annular peripheral surface and the inner annular surface are conical in shape.