When Wally steps out from the water puddle, he takes one step and then stops. The shot then cuts to Spanky, who is sitting next to Wally. When the shot cuts to Spanky, to the right you can see Wally take the one step again.
Although Wally steps into a water puddle and stands in it for several seconds, when he steps onto the concrete, he leaves no watery footprints. (This goof is best seen in the colorized version.)