Do some research on head injuries. Alot of them occur from blows that are not inflicted on the head.
Picture your brain as a big bowl of jello, upside down in your head. It moves a lot like that. Even if you don't take a blow directly on the head, the jello moves/shifts, and slams against the skull. That is what usually cause a concussion.
If you ride any type of "towable", ya it's cool your just being "knocked out". Don't worry about it.
Sorry just showing my hatered towards anything "towable"