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.

A graphic joking about a murdered sex worker, and another about infecting a partner with a sexually transmitted disease were posted on the attraction's Twitter feed.
Critics said the collection of images was sexist and offensive.
Merlin Entertainment said it was "very sorry" for the campaign and has deleted the tweets.
The group said it had wanted to run a "dark Valentine campaign" to promote the London Dungeon, in which visitors are taken on a tour through London's dark history.
But many Twitter users complained that many of the images tweeted were in poor taste and inappropriate for a family tourist attraction.
Rebecca Reid, a columnist for the Telegraph, said: "The biggest issue here is taking violence against women and turning it into a joke or a cheap marketing ploy."
She told the BBC: "Just because these rapes and murders happened in the past doesn't mean they are fair game.
"Violence, rape and murder are all still a very brutal reality of life for modern day sex workers and these flippant tweets show no awareness or respect for that."
Merlin Entertainment said: "Our brand tone of voice tends to divide audiences. However, we recognise that we've upset some people and for that we're very sorry."

Flt Lt Jon Egging, 33, from Rutland, died when his Hawk T1 aircraft - Red 4 - crashed after a display at Bournemouth Air Show in August 2011.
A new display will open at the Bournemouth Aviation Museum which includes a model Red Arrow Hawk T1A.
It will also include a collection box for the Jon Egging Trust, a charity set up in the pilot's memory.
Museum trustee David Shore said: "After running a Red Arrows day last August and the level of interest it generated, we decided we wanted to do something in Flt Lt Egging's memory.
"We had discussions with a model maker at last year's Bournemouth Air Show about creating a display for us.
"The display will have information on both Flt Lt Egging and the history of the Red Arrows with a collection box for any donations to the Jon Egging Trust."
The trust helps young people with vocational and academic qualifications. Its Blue Skies Programme pairs students with role models from aviation, engineering and science.
Bournemouth Aviation Museum's display is the latest tribute in the town to Flt Lt Egging.
In August 2012, a sculpture on Bournemouth's East Overcliff was unveiled featuring three glass Red Arrows planes and stainless steel contrails to coincide with the first Bournemouth Air Show since the crash.
Two deportees who died after jumping from a ferry were trying to swim back to the UK shore, an inquest has heard.
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The London Dungeon tourist attraction has apologised for a promotional Twitter campaign that backfired.
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A new memorial will be unveiled later in honour of a Red Arrows pilot killed in a crash during an air show.