Hyundai Heavy Industries Co., South Korea\'s leading shipbuilder, said Thursday that its second-quarter net profit sank 49 percent from a year earlier as its refinery affiliate suffered a drop in margin in tandem with falling oil prices. Net profit reached 69.3 billion won (US$62 million) in the April-June period, compared with a profit of 136 billion won a year earlier, the company said in a regulatory filing. Sales fell 4.4 percent on-year to reach 13 trillion won in the second quarter, and operating income also plunged 20 percent to 289 billion won over the cited period, it said. Hyundai Heavy, also the world\'s largest shipyard, attributed the drop in net profit to Hyundai Oilbank Co., its refinery affiliate, suffering a drop in profitability. The company also said it built low-priced ships and offshore facilities in the second quarter compared to a year earlier, which also reduced sales.