A man who went overboard from Spirit of Tasmania 1 allegedly screamed for help as passengers watched on in horror.

A large-scale search was launched after passengers on the ferry saw the 45-year-old falling into the water southeast of Port Phillip Heads at 11.40pm on Friday _ a few hours into its voyage from Melbourne to Devonport .

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The search has been suspended.

It’s understood the ship’s crew worked for more than an hour to rescue the man from Bass Strait’s icy waters.

Witnesses told news.com that he was last seen swimming towards the ship, rather than an emergency craft that had been deployed, and was sucked under the boat.

Police said in a statement the decision to suspend the search was based on expert medical advice that the man could not have survived past midday, taking into account various factors including water temperature and weather conditions.

Victoria Police will prepare a report for the coroner.

Bass Strait: water in search area was 12 or 13 degrees. Photo: AAP.

The Australian Maritime Safety Authority (AMSA) coordinated the search with assistance from Victoria’s Water Police and Police Air Wing.

“Two helicopters searched through the night with night-searching capabilities, including the Victoria Police Air Wing helicopter,” AMSA spokeswoman Andrea Hayward-Maher said.

“Unfortunately, they’ve failed to recover the man.”

The Spirit of Tasmania II, which was heading to Melbourne, joined the search, along with two cargo ships.

Ms Hayward-Mayer said the water temperature in the search area was about 12 or 13 degrees.