Sally Hawkins expected someone "better, bigger, shinier" to get her role in 'The Shape of Water'.

Sally Hawkins

Sally Hawkins

The 41-year-old actress portrays mute cleaning lady Elisa, who works at a government research facility in the 1950s and forms a bond with an Amazon sea god shackled in a pool at the laboratory, in Guillermo Del Toro's latest movie, and though she was initially approached for the movie by the director himself, she still didn't think the part would be hers.

She admitted: "I thought it would go away; go to someone much better, bigger, shinier, as they tend to do in Hollywoodland...

"I came to understand that once Guillermo has a set idea, and a vision, and knows who he wants, he's very loyal and you feel like you're part of his family forever."

Sally - who was writing a story about a woman who is transforming into a mermaid when she was approached for the project - found she and the filmmaker had a lot in common, including their aquatic projects and shared passion for film history.

She told the Daily Mail newspaper: "There's a kind of creative soup out there somewhere -- there are moments of synchronicity like that."

As Sally's character in 'The Shape of Water' can't speak, she drew reference from the likes of Charlie Chaplin, Buster Keaton, and Laurel and Hardy for her performance.

She said: "Guillermo was using those silent films as a source for Elisa -- and as far back as I can remember, those same films were big in my life.

"Guillermo and I talked a lot about Elisa having this music in her head, and she dances through life until love takes over her heart . . . and sort of explodes."

The role has landed Sally a Best Actress nomination at the upcoming Oscars, and she's amazed to be in the running again, after previously being shortlisted for her turn in 'Blue Jasmine' in 2014.

She said: "I didn't think I would be at the Oscars once, let alone twice."

But the 'Paddington 2' star doesn't think the recognition means she'll be successful forever.

She said: "You're only as good as the last thing you did.

"These things can go a different way suddenly. One day it's there, and the next it's not. You have to take it with a pinch of salt."