I would never boat in fog on purpose. Commercial fisherman do it all the time - no choice. Furthermore, they know their waters by heart.
Got stuck in a fog bank this morning for an hour or so. Not fun. Where would recreational boaters be without GPS? I do have radar but not expert with it. I am a fair-weather boater. Not in the past, but now.
Navigating In The Fog - When the heat of summer rolls in, humid air and cold water create a dense fog that blankets the coastline.