Last year Dutch and I were not too far from Cape Fair in dense fog, we didn't go far from the launch because of the fog. There was a tourney going on that day and If I remember correctly, it was one of the lower level MLF deals. We had maybe half a dozen boats go by on plane in fog so thick we could not see them. If you know the James channel by Cape Fair it isn't that wide and if you can't see a boat in the middle of the channel, then it is pretty foggy.
I'm guessing that day it was clear at the launch so they let those boys go. Still not an excuse to run on plane if you hit fog.