Guillermo del Toro has revealed that Sally Hawkins had a "massive crush" on the monster in 'The Shape of Water'.

Guillermo del Toro

Guillermo del Toro

The 41-year-old actress stars as mute cleaner Elisa in the Mexican filmmaker's BAFTA winning and Academy Award nominated romantic creature feature, and del Toro revealed he was swayed to pick her as his leading lady after seeing her in Richard Ayoade's 'Submarine'.

But he was shocked by the affection Hawkins developed for the amphibian being on set.

In an interview with Little White Lies, del Toro said: "I saw her in 'Happy-Go-Lucky' and I thought she can achieve this state of grace.

"She is blissful, but alive. Then I saw her in Richard Ayoade's 'Submarine', where she's a secondary character. The way I cast actors is not through the way he or she delivers lines, it's the way he or she listens to the lines being spoken by others. Or by the way they look at the other actor. I just thought, this is it. If I create a great creature and she looks at it like a man in a rubber suit, the film dies.

"If she looks at it like a creature, it lives. She had such a massive crush on the creature. For real. Sally, not the character."

The new film follows mute Elisa who works as a cleaning lady in a high-security laboratory in 1962.

Her life changes when she falls in love with a mysterious, scaled creature from South America that lives in a water tank.

She soon learns that its fate and survival lies in the hands of a hostile government agent and a marine biologist.

But despite Elisa falling in love with the creature, del Toro admitted he didn't want to make a film that could be perceived as controversial due to the unusual plot.

He said: "I didn't want to do a bestiality movie that was perversion and schoolyard gossipy salivation. They just love each other. It doesn't matter that he's an amphibian man or any iteration of the other. The important thing is that they fall in love and they make love. Period."