Water slider for a floor cleaning machine 1, comprising a sliding unit 2 located in front of the brush unit 5 of the machine, characterized by actuating means 3, 6, 13; 3, 6′, 11, 12; 3, 6, 7; 3, 6, 7′; 3, 6, 7″; 3, 6′, 10; 3, 6′, 10′; 3, 6′, 10″ for raising and lowering the sliding unit. The actuation of the water slider can be obtained in several ways: automatically via an actuating bar 3 which connects the sliding unit to the driving wheels of the machine mechanically and which raises/lowers the sliding unit on a forward/backward movement of the wheels; intuitively via a mechanical connection of the bar 3 to the steering handle 8 via a negative gear transmission; manually via an actuating lever 7; 7′; 7″; or by a powered mechanism 10; 10′; 10″ which is steered by the electronics of the machine and which raises/lowers the water slider when the machine is moved forward/backward.