A non-windsurfer would never know how much "wooing" goes on out there on the water. I'm guilty of being a frequent woo-er, possibly an over-wooer. Some windsurfers are never-woo'ers, choosing to grimace and stare straight ahead as they pass sailors on the opposite tack. When I'm wound up, having a great time, and the water conditions are good you're damn right I'm going to woo at my fellow windsurfers. It's an odd form of communication but it universally translate into "I'm stoked!" and occasionally "nice crash, dude!".
The self-woo is a woo of a higher level. If you're alone out there, 50 yards away from anything but the sharks and seals and you woo, then your level of stoke is normal woo times a factor of four. I had a self-woo yesterday at Coyote Point that just kinda snuck up on me. I was planing along on my 5.7 and 104L board, the swell was small and really organized. It was actually the best and most smooth cruising I've ever done in the bay. There was no one around for hundreds of yards and I let out a "Woo!" that only I knew about. It's the equivalent of playing the air guitar in your underpants when you're home alone. It's the normal-woo's better looking sister.