I wave at just about everybody, in any kind of boat, even blowbotes. I try to be friendly on the water hoping it's contagious. (I know, I know, I'm in fantasyland here but I still try).
A few times when I've been out just cruising nowhere and exploring I've come across blowbotes who like to flip me off. So I just either turn around or throttle back and settle in right ahead of them, and let them listen to the exhaust rumble in their faces for half an hour or so. And of course I have to occasionally go to neutral and run the rpms up a little, just to clear the motors of course. After I get bored I go on my way.
Now I fully realize this action does not endear "those awful ceegar boats" into the hearts of these blowboaters, however occasionally, you just have to do something back, to keep your own sanity you understand. Besides these blowhards are gonna hate us no matter what we do, so we might as well do something.
If you're gonna get hung as a horsethief, you might as well ride the friggin horse.