The toy that eventually became known as the Slip 'N Slide was patented in 1961 by Robert Carrier. The first prototype was made of Naugahyd, because Carrier worked at an upholstery shop. Once it was made, he spent time improving the design.
According to Carrier’s 1961 patent , the “aquatic play equipment” was a portable surface for the “sport” of body planing. From his original strip of Naugahyde, Carrier took a ream of the plastic material and sewed a tube into the side, forming an “irrigating duct” to which a hose could attach. The duct had punctures along the length of it, from which water could be released via pressure from the hose. Seams stitched across the length of the fabric at regular intervals also carried water laterally, wetting the repellant surface but not making it soggy.
“It’s very easy to dismiss,” says Walsh. “The best inventions are so simple that people are like, ‘Wow, why didn't I think of that?’ But if you look at the patent, I mean it is really genius. You attach the hose to one end and then sew the other end shut so that there's pressure, and then you put spaces in between the stitches so that water literally shoots out every inch and lubricates the entire surface of the slide.”
But the inspiration for the Slip ‘N Slide was to make things safer for his son. Read the "accidental" origin and the history of the Slip ‘N Slide at Smithsonian.