In a suction dredger or the like, intended for use in ice-filled waters, there is an overflow tube with a stationary lower portion and a vertically movable upper portion. At the lower end of the stationary tube portion, there is a closure member partly covering the end opening of the tube. Also at the lower end of the movable tube portion, there is a closure member, which substantially covers that portion of the lower end opening of the movable tube portion, which corresponds to the portion of the bottom opening of the stationary tube portion being left uncovered by the closure member of the stationary tube portion.
