Pulitzer-winning playright Paul Zindel’s estate has accused Guillermo del Toro of using the late writer’s work without credit for his Oscar-nominated movie The Shape of Water, The Guardian reported. Zindel’s son David told the newspaper that he believes that del Toro’s drama is derived from his father’s 1969 play Let Me Hear You Whisper.

Zindel’s play chronicles the story of a female janitor in a research laboratory who forms a bond with a dolphin and tries to rescue the creature from captivity. Let Me Hear You Whisper was televised in a 1969 movie directed by Glenn Jordan and written by Zindel.

“We are shocked that a major studio could make a film so obviously derived from my late father’s work without anyone recognizing it and coming to us for the rights,” Zindel said in an email to The Guardian.

Producer Fox Searchlight denied the plagiarism allegations in a statement on Thursday. “Guillermo del Toro has never read nor seen Mr Zindel’s play in any form. Mr del Toro has had a 25 year career during which he has made 10 feature films and has always been very open about acknowledging his influences,” the statement read. “If the Zindel family has questions about this original work we welcome a conversation with them.”

Co-written by Del Toro and Vanessa Taylor, The Shape of Water is set in the 1960s and revolves around a mute cleaner (Sally Hawkins) at a high-security government laboratory who falls in love with a captured amphibian creature and attempts to rescue it. The film has been nominated for 13 Academy Awards this year, including best picture, best director and best original screenplay.

The Guardian report observes that similarities between the play and the film include the personalities of their female protagonists and their approach to the creatures they befriend. “The two cleaner characters both learn to communicate with the creatures, and both labs are involved in secretive military operations. The protagonists both discover imminent plans to kill the creature, and both labs mention “vivisection”,” the report says. However, the report adds that there are substantial differences in the endings of the play and the movie.

Paul Zindel, who died in 2003, wrote 53 books in his career, most of them aimed at children or teenagers. He won the Pulitzer prize for Drama in 1971 for his play The Effect of Gamma Rays on Man-in-the-Moon Marigolds.

Earlier this month, The Shape of Water was compared to the Dutch short film The Space Between Us, directed by Marc S Nollkaemper. However, Netherlands Film Academy, which had produced the short film, concluded after a special screening that the two films were distinct, made at different times and “not in any conceivable way interlinked or related”.

The Shape of Water.