I was running a boat(28 Sea Ray) on a sunny day, inside Charleston harbor. We were headed up the Wando river and i got it figured out, so i turn the boat around, only to be greeted by a fog bank that rolled in> i could see the top of the old bridges, but nothing below. I brought the boat off plane and started listening. I could hear a fog horn going off when suddenly out of the fog was the bow of a container ship, I ran 90 off of his course till I was in shallow water, then came about 90 again and creeped along till I could see the base of the bridges. Once I knew where I was, I idled under the bridges(staying out of the channel, but in deep enough water), kept going to i could see the Yorktown, ran parallel to it till I got the entrance to teh marina. The owner of the boat was with me and he was freaking out the whole time, I was a bit nervous my self, but I kept it close and never let on. Once we got the boat tied up and put away, he was asking me how i knew what to do and how to handle it, some how telling him I pulled it out of my *** wasn't going to sound very professional, so i told him I took the power squadron safety course and told him where to sign up and learn more. Sounded good anyways!