Most of the objects I have to avoid when coming into a local harbor don't have AIS, don't have radio, and often have very little clothing on...

The stand up board riders are my greatest "hazard to navigation." In the summer, the yacht basin where I keep my boat is filled with "bodies on boards" all trying to learn how to control the things. Sometimes the sight is quite pleasing to the eye, but none the less, they can be a bit of a navigation issue as they tend to go willy nilly about the channel and the only entry to the basin.