Offshore Coverage from the Mississippi River Delta to Tampa Bay. Detail for Cedar Key area. Soundings in Fathoms. Dont 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 youll love this chart so much, youll buy another just to frame and hang on your wall.