TEN of the 11 Vietnamese seamen feared dead after their ship collided with a larger vessel and sank in the South China Sea early Wednesday were asleep at the time of the accident, their colleagues said yesterday. The 10 crewmen of the ill-fated cargo ship Hai Long were off-duty and sleeping in the cabins, while the 11th missing man, the midshipman, was on deck when the crash happened about 4 am. The 35-year-old navigator, Mr Cao Ba An, the ship's captain and four other off-duty and sleeping crewmen were rescued after struggling in high seas for two hours. One of the crew recalled yesterday how he clung to a floating fridge before being winched to safety by a Royal Hongkong Auxiliary Air Force helicopter. He was taken to Queen Elizabeth Hospital where he is in a fair condition. The five others were rescued by the Panamanian-registered Hing Son, which was dented in the bow by the collision. The survivors spent all day yesterday visiting their colleague in hospital and meeting their shipping company's lawyer and local officials. They are staying at the Mariners' Club in Tsim Sha Tsui. ''It was very dark and suddenly I heard the sound of collision,'' Mr Cao told the South China Morning Post last night. ''It happened so quickly that I found myself in the water very soon, it was so cold.'' Another seaman, 30-year-old Mr Vu Trong Hoanh, said he was woken by the sound of the collision. He was then thrown out of bed, hitting his head before finding himself in the water. Mr Vu was later treated for head and chin injuries at Queen Elizabeth Hospital. The group is hoping to return to Vietnam soon. Mr Cao said their 327-tonne cargo ship was only two years old and loaded with some dry cargo but sank quickly after colliding with the 4,733-tonne Hing Son. Hing Son's captain has been asked to provide more details about the accident. But as the collision happened outside Hongkong territorial waters and involved ships registered in other countries, no full Marine Department investigation will be mounted. Many safety measures are in operation in the sea around Hongkong, but the ultimate responsibility for avoiding accidents lies with a ship's captain or coxswain, according to Marine Department spokesman Mr Peter Choi. ''We have sophisticated state-of-the-art vessel-tracking systems, navigational aids and patrols, but a ship's safety is the responsibility of its master,'' he said. ''The master has to follow the International Rules for the Prevention of Collision at Sea, known as the 'Rules of the Road'. ''We are constantly striving to make Hongkong waters safer and more efficient, and we have a good safety record.'' None of the 11 missing seamen had been found last night and no further searches are planned.