Habib Ullah, 22, has told Fairfax Media how he survived three days in the water while watching his fellow asylum seekers, all men from Afghanistan and Pakistan, drowning one by one.

Mr Habib said the men had seen two or three passing boats, including an oil tanker and a large container vessel, which had not stopped to pick them up. He was not certain if they had been spotted.

On the verge of death, he was finally picked up by a passing Indonesian fishing boat and taken to Jakarta.

The Australian Maritime Safety Authority (AMSA) and the Indonesian search and rescue agency, Basarnas, have separately confirmed that they have no record of the vessel.

But Mr Habib, who is now in immigration detention in Jakarta, has been overwhelmed by distressed relatives from Australia who have heard nothing from their loved ones and are begging him for details.

He said he had paid $US5500 ($5300) to people smuggler Sikander, on the basis of gossip among refugees in Indonesia that ''he succeeded in taking many boats'' to Australia.

They set off in the early hours of October 26 but after about 13 hours of sailing towards Christmas Island, enough to take them about halfway to their destination, the engine and all the pumps stopped.

The satellite phone Sikander provided would not work, so their attempts to phone in their distress to AMSA failed. About 2am the following day, the boat sank.

The asylum seekers, most of whom had personal flotation devices, grabbed ropes to keep together. Mr Habib was with 25 others clinging to one rope.

''On the first day there was hope. Everyone was optimistic,'' he said. ''We were praying, saying there will be an island, there will be a boat.

''On the second day, some people, they lost control, shouting and crying, saying, 'No one will help us.' One guy was in very bad condition. He lost his grip of the rope and went away and he was screaming, crying a few times. After that we didn't hear him any more.

''Then time was passing, night was coming, and the day passing, losing friends. I would see dead bodies coming from the right side, left side. Everyone, one by one, was waiting for their turn because everyone knew that there may not be help, there may not be any chance for a second life.

''Some guys got crazy, they were talking and fighting, they let go of the rope and went away. On the third night there were seven people on the rope, but … in the morning, there were only three people left including me.

''Those guys, their health condition was really bad … one was trying to drown because he was very thirsty and he was very hungry. So he drowned before my eyes.

''On the third day, after they had all died, I was on the ocean from morning to 3pm. I was exhausted, thirsty, tired, hot, pain in my stomach, pain in my kidneys, there was fear of storm, fear of sharks. And I think it was the last moment of my life when the boat came to me.''

Mr Habib was picked up by an Indonesian-based fishing boat, and nursed back to health by the crew before being transferred to a second boat that took him to Jakarta. He is now in the Kuningan immigration detention facility in central Java.

One of the many who have asked Mr Habib for news of their relatives is Australian resident Reza Shafaie, who came to Indonesia to find his cousin, Ali Noori, 17, and uncle, Ali Barati.

Mr Shafaie now believes both died in the sinking, though other families in Australia are not yet convinced.

''They really cry, but they told us to keep searching those areas. They say, 'Maybe there is an island.' Still they have hope.''

Muhammad Rezaie, of Dandenong, also came to search, but he has given up hope for nephew, Enayatullah Hussaini, and friends.

Mr Rezaie, who came to Australia by boat in 2001, said he had begged his nephew not to take the risk. ''I told him, 'The rules have changed, they'll send you to Nauru.' But he didn't listen because his friends push him, 'Let's go together.' The people smuggler was also pushing,'' he said.

Mr Rezaie and Mr Shafaie said they had both spoken to Sikander by phone and he had at first denied their relatives had died, saying the boat was safe on Christmas Island. He later admitted the boat had sunk.