Tubers?! That's freakishly bizarre. I've found the best thing is to stop and motor over to the folks that are getting too close and ask: Do you mind not using our wake for your activity?
It's worked 100% of the time. I've also done that whole yelling thing which seems to just irritate everyone, most of all me!.
In California, we have a general guideline that requires the driver to maintain a safe zone equal to twice the length of the rope. There are also 100 foot restrictions on PWC's for wake jumping.