So, as it currently stands, "surfboard" is implicated to "watercraft," which is implicated to "vehicle." So, adding "surfboard", by a chain of implications, automatically tags the picture with "vehicle," even if nothing in the image actually counts by this site's definition of vehicle. So, my question is, should we de-implicate vehicle from watercraft, under the logic that not all watercraft are vehicles...or we de-implicate watercraft from surfboard, figuring that since it's not a powered device, it doesn't count?

I'd say deimplicate surfboard from watercraft. We don't call parachutes aircrafts, or skis snowcrafts, since they're not designed as transport vehicles (transport aids, maybe, but not transports themselves).

+1 for the removal of surfboard -> watercraft. Considering all watercrafts to be vehicles makes sense IMO.

Sounds good to me! I'll make the BUR.