follow 34 surface movements of the water as the necessary pivotal movement of the arm around the axis 10 occurs float 16 being eccentric to swivel axis 11 also creates a torque which as shown in fig2 tends to rotate arm 4a around swivel axis 11 until the arm abuts stop 17 when the arm is in the vertical position shown in fig2 and 3 when the sweeping movement is terminated as in position iii fig1 the arms must be returned to position i before the next sweeping operation can begin to avoid pushing floating material outwardly from the front of the barge toward the rear during this return movement of the arms they are removed from the water a relatively lengthy operation would be involved in raising an arm around its axis 10 for example by drawing on lifting cable 12 which would also require arm 9 to be moved out of the way and that jets 7 be stopped such a maneuver is executed when the barge is floated but is not desirable in the course of operating the barge instead to remove an arm from the water in the course of work it is swivelled around axis 11 such an operation is shown in fig3 wherein arm 4a passes through position i to position iv shown in broken line to realize this maneuver it suffices to draw on cable 14 which extends between the end of handle 15 and the end of extension 13 fixed rigidly at a.