MARINE Department officers have stepped up their fight against speeding in overcrowded Victoria Harbour, pressing charges against two ferry companies operating high-speed catamarans. One of the two, a Chinese company that operates a service between the Pearl River and Hong Kong, was fined $2,000 after admitting breaking the speed limit. The other is fighting the charge and appears in Tsuen Wan Court next month. The speed limit in the harbour varies according to the size of the vessel, with the average restriction at about eight knots. The large catamarans, however, are allowed to travel at 15 knots, and senior Marine officer Lee Yuk-kwong said it was alleged that the two were travelling ''well into the 20s''. Acting Assistant Director of Marine Barrie Hird said despite the charges against the two companies the number of visible speeders had gone down in the busy harbour since the introduction last month of three high-speed patrol boats. The boats, seven-metre-long Boston Whalers, are bright orange and can travel at up to 38 knots. Mr Hird said their presence in the harbour had made coxswains more cautious. ''Everybody seems to know about them now and speeds in the harbour do appear to have gone down,'' Mr Hird said. ''With our normal launches, you can't really see the Marine Department logo until you get very close. But these are bright orange and it only takes one look for people to know who they are.'' Mr Hird said no accidents or near-misses had been reported in the harbour since the boats went into service on July 1. Mr Lee said the department had also applied for a new radar station on Kau Yi Chau, an island west of Hong Kong Island, to better monitor speeding vessels. ''Checking the speed of ships is different from checking the speed of a car. ''We use data from the radar station plus we have people on the water with stopwatches checking how fast vessels pass from one point to the other. So while the radar will not only be used for this purpose it will help us catch more speeders.'' Meanwhile, a preliminary inquiry is to be conducted by the department into last Sunday's collision between a Hong Kong-Yau Ma Tei Ferry catamaran and a sampan off Macau. Three men were reported missing. Macau Marine Police found the body of an elderly man on Tuesday but two others are still missing.