When operating in fog your biggest danger probably comes from commercial vessels of all types, including fishermen (a BoatTEST.com article). Skippers of these vessels are used to fog and are often complacent, if not downright negligent. (Remember the Block Island ferry which hit the USCG buoy tender a couple of weeks ago?) Commercial fishermen are particularly problematical because they are often short-handed, feel that they know the local waters, and many have a real attitude when it comes to looking out for recreational boaters. You must look out for yourself! In addition to having a high powered radar and keeping a sharp eye on it, going slow, and sounding your horn, we also suggest the following precaution:
When traveling in a busy area, send a securite broadcast. Note your location, speed, direction and any close by navigational aids and broadcast on Channel 16, “Sécurité, sécurité, sécurité, this is the yacht “Wren” leaving Camden Harbor at 5 knots on course 120 degrees leaving buoy R2 headed towards Gilkey Harbor, all vessels take note. The lobstermen will love you, and hopefully, avoid you.
http://www.boattest.com/Resources/view_news.aspx?NewsID=2790