The invention relates to a system (1) for growing plants out of seeds (8) on a water surface, which system (1) comprises:- a buoyant body (2) having a flat bottom surface (5) and a flat top surface (4) parallel to the flat bottom surface (5), wherein the buoyant body (2) is provided with a plurality of passages (3) extending from the top surface (4) to the bottom surface (5)； and- a plurality of containers (7) arranged in the plurality of passages (3), wherein each container (7) has at least a bottom wall (9) with an open structure for passage of the roots (12) of a seed (8), wherein each container (7) has a peripheral wall (10) upstanding along the peripheral edge of the bottom wall (9) and wherein each container (7) has height positioning means for positioning the bottom wall (9) of a container (7) at a set height relative to the bottom surface (5) of the buoyant body (2).
