Tom Hiddleston spent days in a swamp while filming Kong: Skull Island

Tom Hiddleston found filming in an untouched region of Vietnam for Kong: Skull Island to be physically challenging.

The British actor plays Captain James Conrad, a Special Air Service (SAS) tracker who is hired to go to a deserted island on a mission to find the giant ape, with the cast also including Samuel L. Jackson, John Goodman and Brie Larson.

The stars flew to many different locations during the shoot, including a remote place north of Hanoi in Vietnam, where they had to film in a swamp for ten days, and Tom admits that sequence was tough.

"It has its challenges," he said at the film's London premiere. "There's a swamp in Vietnam that we ran through every day for ten days which was almost as cold as (current British weather)... The thing about the swamp is that it (the film) requires you to get back into it and however wet you get the first day, for continuity, you have to get that wet for the next ten days."

Despite that downside, Tom insists it was "fun" and "felt like adventure" to be filming in exotic locales.

And he felt privileged to be shooting in an area that was "completely untouched, completely unspoiled" and to be welcomed by the locals.

The 36-year-old signed on to appear in Kong early in the development stage which meant he got to make small suggestions about his character during the rewrite stages. For example, Tom felt that James should be in the SAS to differentiate him from Samuel's U.S. Army Lieutenant Colonel.

"I just sort of chipped in with things I found interesting, suggested that perhaps the character should have been in the SAS and that he would be from a different military unit to Sam Jackson's character because they have a difference in opinion," he explained.

Kong: Skull Island hits cinemas from 8 March (17).