Soleymani says that Operation Karbala-4, which was an Iranian offensive in the Iran–Iraq War on the southern front, has inspired the original idea of the film.
According to the memories recalled from the comrades, there was a big tunnel to be dug as a resort in between Operation Karbala-4 and Operation Karbala-5 since there were enough martyrs already during Operation Karbala-4.
“And ‘Snorkel’ is the story of this tunnel and how it was exposed; and also the story of a warrior who has been taken captive and now his sister is back after 30 years and is told that her brother is not martyred,” explains Soleymani.
Operation Karbala-4 was launched under the cover of darkness in late December 1986, and was meant to give Iranian forces a foothold along the Arvand Roud waterway in the country's southwest.
However, the operation did not go as planned. The deposed Iraqi Ba’ath regime was notified of Operation Karbala-4 mainly through US intelligence operatives.
As many as 175 bodies of the divers, who were reportedly buried alive with their hands tied with wire, were unearthed in early June, 2015.