Had an interesting time going south on Winyah Bay a few years ago having fog so thick it was the same problem. Couldn't see 50 feet. We were moving on radar and chartplotter making 3 knots on the big bay when a blip appeared to be closing in at us at a fairly high rate of speed, AHHHHHH!. We stopped the boat and the other boat also stopped. We moved along slowly with this thing closing in on us again.
Found out it was a 40' power vessel that had stopped and wasn't moving at all because he had no idea where he was. It was us closing in on him. As we slowly motored by him he asked if he could follow us. "Sure, we're headed down the bay and back to the ICW." By the time we turned right onto the ICW we had 4 power boats following. It was a lot of fun for us as it was the first real test of our Raymarine C-series. We were like some kind of Mother Hen with her ducklings in tow.
Soon after we turned on to the ICW, the fog started clearing and the 4 boats roared past us throwing a 4 foot wake, dumping everything in the galley on the cabin sole.,,,, THANKS GUYS!