Ha Long Bay is Vietnam's biggest attraction, one of the most magnificent natural splendors of the Far East. ''Ha Long'' means ''Where the Dragon Descends into the Sea''. From the emerald-green waters of Ha Long Bay some 3000 limestone and dolomite islands (. or ''grottos'') rise jaggedly from the Gulf of Tonkin like medieval stone cathedral spires, or the scales on a dragon's back. Local lore has it that an enormous dragon created the bay, grottos and outcroppings as it thrashed its way toward the open sea to prevent the intrusion of enemy navies. Today, local fishermen still report encountering a giant sea beast called Tarasque, sort of the Nessie of the South China Sea.