A WOMAN died and two men were missing presumed drowned last night after their pleasure boat rammed a buoy and sank off Chek Lap Kok. A third man, Cheng Kit-wai, 22, was rescued after almost five hours in icy waters and later joined the search for his missing friends, Wong Wai-hong and Lai Chun-yu, both 18. The body of Tang Suk-kwan, 26, was found 10 hours after the accident. It emerged last night that a helicopter had not been sent to the scene for more than an hour after the authorities were alerted, because they wanted to check the call was not from smugglers attempting a decoy. The search for Mr Wong and Mr Lai was called off at 9 pm yesterday and will resume this morning. Mr Cheng, Mr Wong and Mr Lai, from Tung Chung on Lantau, had arranged to make the trip from Yuen Long to the waters north of Lantau with Tang and several other friends on Christmas Eve. The other friends did not show up. The six-metre boat hit a buoy after midnight and sank. All four were thrown into the sea. Mr Cheng used a mobile phone to call Mr Wong's brother, saying the boat was sinking after hitting an unlit buoy near the Brothers Islands. The boat was below water within minutes, he said. 'I had no chance to grab a life jacket because I was phoning for help, but the others took life jackets before they fell into the water,' Mr Wong's brother quoted Mr Cheng as saying. Tung Chung villagers took a speedboat to the scene after receiving the distress phone call but found nothing. Police were told at 12.24 am and said their small boat units arrived on the scene 16 minutes later. A Marine Department spokesman said a helicopter was not called straight away because officers had to determine whether it was a bona fide SOS and assess the situation. Wong Wai-hong, another brother of Mr Wong, said: 'They did not respond immediately to our call, because they thought we were smugglers.' A Government Flying Service helicopter joined the police launches and fireboats in the search at 1.35 am. The Marine Department asked nearby vessels to look for wreckage or survivors. Shortly after 5 am, Mr Cheng was spotted hanging on to a chain at a Tsing Chau Wan floating dockyard near Yam O, Lantau Island, and was rescued by a passing vessel. He discharged himself from Tuen Mun Hospital against medical advice and joined the search. At 10.30 am, the body of Tang, wearing a damaged life jacket, was found 45 metres off Yam O. Tang, a cosmetics saleswoman, lived with her parents and brothers in Tuen Mun. Relatives said she left home for the boat trip after having a Christmas Eve hotpot dinner with her family. The Marine Department said it was not clear whether the boat had strayed into restricted areas off the airport site. A spokesman said all vessels were prohibited from passing near construction areas off the site. 'There has been some marine work going on for months, during the duration of work at the new airport,' he said. 'We are aware this type of marine work is dangerous. That's why we put out notices and broadcasts.' Buoys mark the marine work sites and notices have been sent to the shipping community informing them of the restricted areas. These were reinforced by radio warnings each morning, the spokesman said, and boats caught flouting the notices had been prosecuted. The $60,000 vessel was bought by the three men about a year ago. The Marine Department said all boats should have the proper safety equipment. The spokesman said: 'They should not have to make distress calls by mobile phone, but by radio. It's also important they have experience of the sea.'