On a slight tangent, but somewhat related...
A couple of years ago, we wanted to make a passage of about 75nm down the south western coast of Sweden. It was one of those end-of-holiday-had-to-be-back-to-work scenarios. We were about to give up on this passage because of the unsuitably high waves that day. Just as we were making this decision, along comes a slow-moving freighter which, according to the AIS was headed to the same destination we were. I thought I'd see what the ride would be like following the freighter, relying on him to be a "wave breaker". It worked out well, following at about the distance you can see in the photograph. I didn't especially like doing this, but the risk seemed minimal at the time. I thought of radioing the captain to see if he minded, but I didn't. He didn't radio me either. The crew knew I was there, as I could see them on deck. Nobody waved me off. Furthermore, we were broadcasting a class B AIS signal, so the ship likely could have seen us that way as well (unless they had filtered out Class B signals).
Would I do this again? Based on my experience on this run, I think so, as it all seemed to work out well. I'm curious as to what others on the forum think...