Using too much water to douse the fire aboard the Mega Borg could sink the oil supertanker, but firefighters using foam to smother the flames today faced another problem, salvage experts say. ``You have to get on that ship to extinguish it,'' said Les Williams, whose Port Arthur, Texas, salvage company has fought nearly two dozen offshore oil fires. ``If the fire's below deck, it's like trying to walk on a hot skillet. You can't do that.'' The fire burned since Saturday aboard the 853-foot Norwegian ship, crippled in the Gulf of Mexico 57 miles southeast of Galveston. It started with an explosion in the engine room on Saturday; five blasts Sunday sent blazing crude oil from the tanker's 38-million-gallon cargo into the sea. ``That's a very hard fire to fight, there in the engine room like that,'' Rudy Teichmann of T&T Marine Salvage Inc. in Galveston said. ``It's all closed up and you can't get to it. ``They can't flood that engine room with water. That could sink the ship. It's a lot different than fighting a forest fire,'' said Teichmann. The Mega Borg already was listing. Its stern dropped 58 feet since the first explosion, indicating either the cargo had shifted or the ship was taking on water, the Coast Guard said. The aft deck was reported just 5 feet above the water today. About 30,000 gallons of foam has been shipped to the scene, the Coast Guard said. But using it entails firefighting at close range. Wiliams said the usual procedure is for two or three firefighters, wearing fire-retardant jumpsuits that are light enough to swim in, to board the tanker. Carrying a 3-inch diameter hose leading to foam pumps aboard a nearby boat, they target the fire's point of origin, he said. The hose, or ``wand,'' can shoot 5,000 gallons of foam per minute. Attempting the job is Smit American Salvage Inc., the U.S. division of a Rotterdam company. Smit has helped fight more than 100 tanker and oil rig fires, including blazes in the Persian Gulf during the Iran-Iraq war, company officials said. Steve Davis, captain of the 180-foot supply boat Tradewind, and his crew of four spent Sunday loading drums of chemical foam on board the boat to fight the Mega Borg fire. ``I would hate to see oil all over these beaches,'' Davis said as specialists from the Netherlands finished bolting high-powered pumps and nozzle connections to the ship's deck. Davis' boat is one of six from Pelican Island near Galveston that were hired to fight the fire. ``God willing and weather permitting _ that's the saying in salvage,'' said Rick Chianelli, salvage foreman for Smit American.