The movie's marketing had film posters celebrating the marines as the "Canoe Commandos".

Vivienne Knight in her Trevor Howard biography 'Trevor Howard: A Gentleman and a Player' states in relation to this movie that " . . . the Portuguese government had decreed that filming in Portugal for this movie would have to stop unless the film company guaranteed to make a documentary about Portugal to be shown with 'Cockleshell Heroes'. It was a rare stab at blackmail coming from any government, particularly as it must have been obvious that, once the film was sold for distribution, nobody could possibly guarantee that another film would be shown with it. However, Euan Lloyd Warwick Pictures production assistant was not about to argue. He had been deputized to write, produce and direct the documentary; he also got the excellent second unit cameraman, Ted Moore, who later won an Oscar for A Man for All Seasons. Trevor Howard volunteered to do the commentary. The schedule was arranged to give Trevor two free days and the unit of three went off to shoot footage of caves and any other points of interest they could find. They also found the famous fado singer, <a href="search.php?q=Amalia+Rodr%C3%ADguez&submit=OK

This movie had three working titles. They were: 'Survivors Two', 'Canoe Commandos' and 'The Survivors'.

This movie's budget was considered expensive during the era in which it was produced.

Second film directed by José Ferrer.