And people kayak out there
I had that almost happen to me a couple years back when I was fishing in my kayak anchored, in the back of a large cove.
The boat only had one guy in it, but he was messing around with something in the back of the boat while the boat was steering into my direction unattended.
I almost bailed but I hollered loud enough he heard me. It was only trolling speed, but it would have done a number on me had I not been watching him.
Just another reason to carry one or two of those air horns.
All you have to do is stand around a boat launch on a weekend, and watch people launching and loading their boats just one time, and you will understand how that kind of stuff happens.