I was really thinking about recreational boats. I ve tracked echos running 20kts or more approaching passing so close that I only saw them for a couple of seconds on 100' VIs.
But yes, the fast ferries are even more scary. While I could undestand thm running fast in open water, they should go slow while in chanels. I once came in Hyannis in conditions where you couldn't see anything whileA fast ferry was charging at full speed in th opposite direction and as you know, unlike nantucket, hyanis is not a straight shot.