It has been almost a week since Mohamed Isa Omar was pulled from the freezing waters of the Channel, one of only two people to survive the deadliest crossing on record.

But as he sits in a wheelchair in a French car park, the 28-year-old is clearly still traumatised. He speaks softly, telling the BBC he is haunted by what he saw that night.

“I saw people dying in front of me,” Mohamed says. “Those of us who could not swim, drowned and died within minutes.

“It was so cold the water, so cold.”

Mohamed was among at least 29 people who set off from the coast of France at about 22:00 local time (21:00 GMT) a week ago. The other occupants were strangers to him – simply more people willing to risk the dangerous crossing over the Channel to reach the UK, a journey made by more than 25,000 migrants this year.

They had been travelling for about three-and-a-half hours when the boat started to sink, Mohamed said.

At this point, the occupants who still had phones began to make desperate calls for help. A fellow survivor told Kurdish media they had called both French and English sides of the Channel.

“Our mobiles were already in the water,” Mohamed recalls. “But one of us had his mobile still working, he called, and the [British] authorities told him to send the location.

“But before he does that, the mobile went into the water too and we could not send anything.”

Mohamed heard a second man make a call via speakerphone, saying the person at the other end spoke English.

“But he also didn’t have any chance,” Mohamed told BBC Persian. “The water got his mobile too before he sends anything.

“That’s why people started to drown and die. I saw people dying in front of me, but I started to swim. I saw a big ship far away and started to swim towards it.”

It would be hours, though, until Mohamed was rescued. According to the only other survivor, an Iraqi Kurd named as Mohammed Shekha Ahmed, a number of people tried to cling onto the deflated boat until the sun rose.

“Then when the light shone, no one could take it any more,” he told Iraq’s Rudaw network.

Their bodies were spotted by a French fisherman at almost 13:00 on Wednesday. A rescue operation was launched, but the two men were the only ones left alive.

“That’s why they found their way to us, took us to the hospital, and we were saved, thanks be to Allah,” Mohamed said. His legs are bandaged, recovering from injuries sustained during hours at sea.

All of the names of those who died are not yet known. Only one person has been officially named: a young woman hoping to reach her fiancé. Among the missing are a mother and her three children – including a little girl who was just seven years old.

Both the men who made the calls died, Mohamed said. It is unclear who they reached when calling for help, or where they actually were.

The remains of the boat and its occupants were in French territorial waters when the Coastguard was asked for assistance.

A Home Office spokesperson said: “The French led a search and rescue operation for an incident that occurred in French territorial waters on Wednesday 24 November, where 27 people tragically died.

“As part of this operation, the French requested support from the UK, which was provided by HMG Coastguard as soon as it was requested.”

A Maritime and Coastguard Agency spokesperson said that on that date, they received “more than 90 alerts, including 999 emergency calls, from the English Channel, and we responded to all of them”.

“HM Coastguard does not routinely enter French waters unless asked to assist with a response by our search and rescue partners in France, as we were last week,” the spokesperson told the BBC.

“On that occasion, we sent HM Coastguard’s helicopter from Lydd to support the search and rescue effort and the RNLI lifeboat from Ramsgate also participated in the search.”