Cochrane reveals in an extract of the book published by the Daily Mail, that the desperate rescue attempt called for drastic measures - including lies about what the rescue involved.
Worried parents were assured that their sons would swim to rescue and be guided with an airhose, but according to Cochrane, "this was untrue".
Due to their inexperience as swimmers and divers, the mission could have been fatal.
Cochrane writes: "The only hope was to sedate them, put oxygen-fed masks with silicone seals over their faces and let the expert cave divers carry them out."
Describing the rescue of one boy, Note, Cochrane reveals, "The divers then handcuffed him, tying cable ties around his wrists and clipping them behind his back" so that he couldn't accidentally rip off his oxygen mask during the risky mission.
Australian diver Dr Richard Harris was called in, being highly experienced with anaesthesia. Cochrane writes that Dr Harris put the boys to sleep, while his friend and diving partner Craig Challen had the job of checking on the boys as they were swum out.
In his book, Cochrane details that Harris and Challen previously practised the escape plan alongside Thai Navy SEALs, using young boys of a similar size as "dummies".
"They practised putting masks on them, submerging them face down, with a diver holding them underneath and passing them through the water. The youngsters were told to stay still, like the soon-to-be-sedated Wild Boars."
And the plan worked - with all 12 boys eventually brought to safety.
Tragically, Navy SEAL Saman Kunan died during the rescue mission from a lack of oxygen, but the boys and their coach paid tribute to him after learning of his death.