Not being a stand up bass player, or a violinist, I can only surmise what the freedom tinged with challenge playing a fretless string instrument would be like. And yet, I instantly related to mat surfing in those terms.
The most obvious analogy to a fretless instrument would be a "finless" surfcraft, which of course would include matting. But there's something deeper to this idea as it pertains to mats, which I can't really put my finger on.
Additionally, mat surfing is devoid of the ''fret'' associated with conventional surfing, in terms of competing for "good" waves in a crowd. So it works on that level to.
I wish I had more to say, but I don't. Please share your thoughts in the comment section, and maybe we can round out this concept.