Leading Seaman Faye Turney has told how she "felt like a traitor" when she was forced to write "confession" letters shown on Iranian television.
Faye Turney has reportedly struck a deal worth more than £100,000
The only woman among the 15-strong Royal Navy crew has also defended her decision to sell her story to ITV1's Trevor Macdonald and the Sun newspaper.
Some of the reported six-figure sum for the interview will go to navy families.
Relatives of soldiers killed in Iraq have criticised the decision allowing the crew to sell their stories.
Lord Heseltine, the former deputy prime minister and defence secretary, has called for an inquiry into the decision to allow the sale of stories.
And Lieutenant Felix Carman, who was among those held, has said he finds it "unsavoury" that his fellow captives are being paid to tell their story. But the Sun newspaper has defended its decision to pay Leading Seaman Turney for her story.
The paper's defence editor, Tom Newton-Dunn, who refused to reveal how much she was being paid, said: "She has a right to do this. We are a free country. Faye has been through the most extraordinary ordeal, which is clearly graphically illustrated."
In an interview broadcast on ITV1's Tonight with Trevor Macdonald, Leading Seaman Turney said she was told she would be charged with spying unless she wrote the letters shown on Iranian television.
In one letter, she criticises the Bush and Blair governments for intervening in Iraq.
"When they wanted me to write what was written about the British and American troops I felt like a traitor to my own country," she says.
In the programme, she defended her decision to sell her story and says a percentage of the money will help the crew and families of HMS Cornwall.
"I was offered a hell of a lot of money for my story. I've not taken the biggest offer, I've gone down...because I wanted to speak to yourself and the Sun because I knew my point would be put across.
"I want everyone out there to know my story from my side, see what I went through," she told the programme.
Asked what form her interrogation took, she said: "It took two forms: you had Mr Nice Guy who wanted to be your best mate; he was concerned at the fact that I hadn't been eating.
"And then you've got the guys who were like, 'Do you want to see your daughter again?' And that's the way they use that against you. And that was horrible."
She also described how at times during her two-week ordeal, she cried herself to sleep.
In a separate interview with the Sun, Leading Seaman Turney said she feared her Iranian captors were measuring her for a coffin before killing her.
Her captors asked how she felt about dying for her government and never seeing her daughter again, she said.
Leading Seaman Turney, known as Topsy, said her lowest moment came when her captors isolated her from her colleagues and told her they had been sent home.
"All I could think of was how completely alone I was. They could do anything now and nobody would know," she told the Sun.
Meanwhile Arthur Batchelor, 20, the youngest of the British sailors to be held captive, told the Daily Mirror about his "nightmare" at the hands of his captors and how he "cried like a baby" in his cell.
He told the newspaper: "A guard kept flicking my neck with his index finger and thumb. I thought the worst, we've all seen the videos. I was frozen in terror and just stared into the darkness of my blindfold."
The crew returned to the UK on Thursday after 13 days in captivity
Both of the officers among the captives have said they do not plan to profit from the story.
Royal Navy Lt Felix Carman said any fee was likely to go to charity.
"I am not interested in making money out of this," the 26-year-old from Swansea told the BBC.
"My main aim is to tell the story. There's some people who might be making money, but that's an individual's decision, that's very private."
Captain Chris Air said that he did not plan to sell his story but insisted his fellow service personnel had the right to.
The MoD said its decision would ensure officials "had sight" of what might be said as well as ensuring "proper media support" to the captured crew members.
Sally Veck, whose 19-year-old daughter Eleanor Dlugosz was killed in Iraq, criticised the MoD for letting the sailors and marines profit from their ordeal.
She told the Times: "If you are a member of the military, it is your duty to serve your country.
"You should do your duty and not expect to make money by selling stories."
The sailors and Royal Marines were held after Iran accused them of entering its waters, a claim they denied.
The MoD has said experiences of the navy crew amounted to "exceptional circumstances" that allowed its usual ban on such payments to be lifted.
Maj Gen Patrick Cordingley, who led the Desert Rats in the first Gulf War, said he was "depressed" by the decision to sell stories as they had "not overplayed their experiences" in the press conference which took place when they returned to the UK.
He said the Ministry of Defence or the government seems to be "manipulating this whole particular process" for propaganda purposes.