India, March 30 -- Venkatrao Jammu realised the brutal reality of an Iranian prison not through a warning, but through absence. One morning at Bandar Abbas City Central Jail, the 35-year-old third officer woke to find the adjacent bed empty.

"I asked a roommate what had happened," said Jammu, a seafarer with 17 years at sea. "He said the man had been executed. I had only asked out of curiosity. I did not expect that answer."

Jammu was among 18 Indian crew members of Valiant Row, a cargo vessel operated by Dubai-based Global Tankers Private Limited, who were detained by the Iranian Navy in December last year after their ship was intercepted in international waters and taken to Iran's port city of Bandar Abbas. On March 29, the seafarers ...