Having fun on something behind the wake of a power boat has made many smiles. Whether it is a knee-board, water ski, or foil board, there is just something awesome about the feeling.

One of ZUP's patents was 8,292,861 (see figure below), protecting an aspect of their ZUP board.
The independent claims of ZUP's patent essentially protected the combination of the following elements (at least according to the Federal Circuit): (1) a riding board; (2) a tow hook on the front of the riding board; (3) a plurality of rails on the bottom surface of the riding board; (4) side -by-side handles on the front of the riding board; (5) side -by-side foot bindings on the middle of the riding board; and, at least as stated in claim 1, (6) the ability to simultaneously engage the handles and foot bindings to position the rider in a crouching stance.
Nash, likely seeing the ZUP board, came out with a similar looking design, shown below

The question that is always difficult to answer for those alleging obviousness is - if it was so obvious, why didn't anyone every do it? There was clearly a market, which ZUP proved. But alas, that is that difficulty in analyzing obviousness.
So, what could ZUP have done? One issue to note is how similar the products actually appear, leading one to wonder whether a design patent might not have come in handy in this case.