Fishermen who flock to North Carolina's coast have only recently discovered that some of the best fishing for big king mackerel can be found in a bad place-the "bad bottom" off Cape Hatteras. You can troll for kings with spoons or lures, but the most productive method by far is slow-trolling or drifting live baits-menhaden in particular-using 20- to 30-pound-class spinning or bait-casting tackle. It's not unusual for a day's catch to include a dozen fish over 15 or 20 pounds; a 30-pound fish doesn't raise eyebrows anymore. An area that covers between 10 and 15 square miles of the Atlantic Ocean, the bad bottom is a series of rock and reef outcroppings in 50 to 70 feet of water. The area extends from just southeast of the "diamond shoals," off the town of Buxton, south to an area that's six to seven miles south of the town of Frisco, and it starts within four or five miles of the beach. The nature of the ocean floor rules out a lot of commercial trawling in the area, but it's perfect for holding baitfish, and in the fall that means it also holds king mackerel. The fishing can be so good, in fact, that the extensive charter-boat fleet working out of Hatteras often leaves the blue waters of the Gulf Stream-and the tuna, dolphin, wahoo and billfish-and stays inshore for weeks at a time. The best inshore fishing usually starts in the early part of this month, and depending on the unpredictable autumn weather, it can last until almost Thanksgiving. Contact: North Carolina Marine Fisheries Division, Morehead City (252-726-7021); Hatteras Harbor Marina (252-986-2166); Oden's Dock (252-986-2555).