For narrow channels I station my wife on the bow with an air horn and she lets them know we can't yield or stop. Once I had a Chesapeake Bay Foundation john boat ask me if I would have run him down. The response was a simple "Yes".

I have a local kayak club near me. Some of them are beautiful wood ones and the varnished wood almost impossible to see in choppy water. When I ask why they don't at least use red or yellow paint on the paddles so they have a chance of being seen in the choppy water with boats of all sizes speeding on the river they give me a dumb look like it is my job to keep an eye out for them and avoid them. If I have a hard time at six knots what is it like from a Donzi at 40+? Also they seem to prefer mid channel to staying in the shallows.

Of course we have to remember the jet skis that cut right under the bow. Here I hope I can get the registration number to make it easier to sue the estate for damages and the haul out.

As nat says "Speed Bumps" or I prefer "chum".