a canal paving machine is described . the machine comprises an elongated frame which extends transversely across the canal and which is propelled the length thereof while water continues to flow in the canal . a concrete paver is supported on the frame and is designed to lay concrete on one of the sides of the canal and at least a portion of the bottom of the canal as the frame is moved along the length of the canal . dam members encircle the concrete paving apparatus to protect it from water flowing in the canal during the paving operation .