Aquaboard

On his recent trip he confined himself to driving a runabout, towing Lynda Bird on an aquaboard, trying rather unsuccessfully to teach her to ski.

Source: wiktionary

No person shall operate a personal watercraft to tow a water skier, aquaboard or other similar device unless there is in such vessel a competent observer, in addition to the operator, and the personal watercraft is designed by the manufacturer to carry the operator, the observer and the person(s) being towed.

Source: wiktionary

I don't know how much he had left, but it was enough to continue living in a large penthouse in what was once his prideful project, to have a lively summer place on Tupper Lake — where I learned to ride an aquaboard behind his Cris-Craft (was it cold when we fell off into the lake!) — and in general to live in ample luxury with his large family.

Source: wiktionary

The rope used had to be long enough to get the aquaboard rider well away from the propeller—fifteen feet was a good length. A ride started with the motorboat slowly gaining speed and the rider lying down flat on the board.

Source: wiktionary