HONGKONG-based Halvorsen Marine has announced that its associate company Shenzhen Jiang Hua Marine & Engineering in Shekou has sold 12 high speed ferries in the mainland market. Mr Harvey Halvorsen, vice-chairman of Jiang Hua, said the company, which has delivered 12 units since October 1992, had many more orders in hand. ''These 42 ft, high-speed fibreglass ferries, carrying 40 to 46 passengers at 30 knots, are powered with twin 200 horsepower diesel engines,'' he said. The vessels, which provide fast and economical travel in the Pearl River delta area, offered excellent returns to operators for a relatively low capital investment, he added. The vessels were designed in Shanghai and built to Chinese commercial standards. Jiang Hua also has been the builder of Halvorsen Marine's world-renown island Gypsy line of pleasure boats since 1980.