Hyundai Mipo Dockyard Co., a unit of the world's biggest shipbuilder, Hyundai Heavy Industries Co., said Tuesday that its second-quarter earnings plunged 51.2 percent from a year earlier due to decreased orders. Net profit came to 88.6 billion won (US$82.7 million) in the April-June period, compared with a profit of 181.6 billion won a year ago, the company said in a regulatory filing.