Panel for floating cultivation of plants on water, including parallel grooves at a top side extending longitudinally, adapted for receiving a substrate and a number of plants or precursors in the substrate, each groove extending through the panel from a first top plane to a second parallel plane. The panel includes air chambers at a lower side extending substantially below the second plane, each of the air chambers allowing therein formation of air roots of plants supported in the substrate of the grooves. At the second plane, each groove is spaced apart from the circumferential side wall of the air chamber it debouches in when projected onto a plane normal to the longitudinal direction, each of the grooves including at least two side support surfaces extending parallel to the groove and below the top side, the side support surfaces adapted for substantially completely supporting the substrate in the groove.