Offshore Coverage from the Mississippi River Delta to Tampa Bay. Detail for Cedar Key area. Soundings in Fathoms. Don’t go venturing offshore without this Northwest Florida nautical chart. Navigate with ease through the offshore region from the Mississippi River Delta to Tampa Bay. Spend a Saturday cruising singular Key (Cedar Keys) as well. For your convenience, soundings are in fathoms. We bet you’ll love this chart so much, you’ll buy another just to frame and hang on your wall.