The 23-year-old also says he saw for himself "how 10 of us, including women and children, died of starvation" while being stranded on the boat for months.
Razali Puteh, the fisherman who first spotted the migrants, said he and others were fishing about 60 kilometres off the coast of Indonesia's Aceh province when they saw the overcrowded trawler about three kilometres away.
"When coming close, I was very surprised with what I saw on the boat," he said. "It was crammed with people ... I was speechless and breaking down into tears when watching them screaming, waving hands and cloth."
He says: "I could not have let them die, because they are also human beings, just like me. I am grateful to be able to save hundreds of lives.