A water-resistance rowing machine has a frame body, a water-resistance unit, at least one blade wheel, a pulling strap, and a seat. The frame body has an elongated beam and a pulley rotatably mounted on the frame body. The water-resistance unit has a water tank extending along the elongated beam, a rotating shaft disposed in the water tank and extending along and being parallel to the elongated beam, and a strap wheel assembly connected with the rotating shaft to drive the rotating shaft to spin. The at least one blade wheel is mounted on and rotated with the rotating shaft. The pulling strap is wrapped around the pulley and has an end connected with the strap wheel assembly and a handle formed on another end of the pulling strap. The seat is mounted on the elongated beam.