The day I bought my first kayak, I had to make several stops on the way home and I realized there was nothing to stop a miscreant from taking it off the roof of my Explorer. After my first paddle, I immediately set out to make it theft resistant.
I had an idea was that a vinyl clad steel clad cable would be ideal for securing the kayak. This left me with two questions to answer: How do I connect the cable to the kayak, and how to I secure the cable to something?
I looked my kayak over, and then took a look at other models and decided that all kayaks are divided into two groups: those with something permanent to connect the cable to and those without.
My first kayak was a Perception Swifty; the seat was molded out of the same piece of plastic that the hull was. A cable wrapped around the seat support in that type vessel (or through the hull, as would be the case with a sit-on-top) cannot be removed without tearing up the boat or cutting the cable. If you have ever tried it, you know how hard that is.