Albanians Artur Doda, 24, and Leonard Isufaj, 27, leapt from the Stena Britannica, off Harwich, Essex, on 26 February last year.
The pair had tried to enter the UK hours earlier inside a lorry, the inquest into their deaths in Chelmsford heard.
Coroner Eleanor McGann recorded conclusions of accidental death.
Mr Doda and Mr Isufaj were among a group of 15 people from different countries caught in a random x-ray check at Harwich before making it into the UK.
The inquest heard Mr Doda was sliced by the "machete-like" motion of the ship's propeller while Mr Isufaj drowned.
Both men were sucked underwater almost immediately after they jumped over the side of the ship, ten minutes into its journey back to Zeebrugge, Belgium.
Essex coroner Ms McGann said: "The evidence suggests they were intending to swim back to England, something that they could see was tantalisingly close to them."
Insp Christopher Willis, from Essex Police, told the hearing the sea would have appeared deceptively calm to the men.
"To swim to land with those tides and the water temperature would have been nigh-on impossible," he said.
"An Olympic swimmer would have struggled."
Speaking after the hearing, Mr Isufaj's cousin, Besnik Vata, 33, from north London, said the case highlighted the plight of many immigrants.
"We heard that they weren't escorted on board the ship so there was always a risk this would happen - if I was in that position I would have done the same," he said.
Border Agency official Giles Young said there was no policy of escorting deportees in place.
Two deportees who died after jumping from a ferry were trying to swim back to the UK shore, an inquest has heard.