Girl meets hot fish monster, falls in love, plots to break him out of a top-secret government research facility. On paper, Guillermo del Toro’s fantasy-sci-fi-romance-thriller The Shape of Water looks a bit Splash-meets-ET – with the addition of an interspecies sex scene. (And you know Steven Spielberg and Ron Howard would never have gone there.)

As Oscar bait, this film is a tough sell. For starters, it’s the wrong genre. Academy voters rarely put a tick for best picture next to films featuring big beasties, let alone a film with an orgasming big beastie. (The only fantasy film ever to win best picture was The Lord of the Rings: The Return of the King; a sci-fi has yet to scoop the prize.)

Del Toro’s fish movie ought to be the Oscar race’s rank outsider. Instead, not only is it bookies’ second favourite for best picture (a fin or two behind Three Billboards Outside Ebbing, Missouri), it boasts 2018’s biggest haul of nominations, with 13.

Sally Hawkins should (but likely won’t) win best actress for her role as Elisa Esposito, a Baltimore cleaning lady who works the night shift in a bunker-like government lab in the early 1960s. Unable to speak (abused as a child, her vocal cords were cut), Elisa uses sign language to communicate. The moment she claps eyes on her 7ft-tall lizardy beau in a murky tank, she’s smitten. (Not convinced? Wait till you see him; he’s a shimmering beauty.)

The last of his species, Amphibian Man (to use his official name in the credits) was captured in the Amazon, where the indigenous people worshipped him as a god. Now American scientists are experimenting on him like a lab rat. Prodder-in-chief is security boss Strickland (played by Michael Shannon in another one of his juicy Mr Nasty roles). To plot her daring rescue, Elisa enlists her only two friends in the world: gay neighbour Giles (Richard Jenkins) and chatterbox work pal Zelda (Octavia Spencer), who asks the question we’ve all been burning to about Amphibian Man’s particulars. (“How? Does he have a … ?”).

Even if you don’t find the idea of fish sexy, or, like me, have been on the fence about Del Toro in the past, this is a movie that might well find its way into your heart. It’s beautifully acted. Hawkins is dazzlingly good as Elisa. As critics have pointed out, she plays the role like one of the all-time silent-film heroines. And at a time when everyone is banging on about strong female characters, her performance says something nuanced about strength: Elisa’s vulnerability isn’t a sign of weakness. There is inner steel in openness, allowing the world to see who she really is at her core, without putting up a tough wall of cynicism or world-weariness. Kudos, too, to Del Toro regular Doug Jones, who plays Amphibian Man (it took four people and tubs of lube to squeeze him into his latex suit every morning).

For better or worse, this is a film that only Del Toro could make. He’s always had a thing for monsters. (In Mexico as a child, his Catholic grandmother tried to exorcise him, twice.) And after bigger budget pictures like Pacific Rim and Crimson Peak, The Shape of Water is a return to more artisanal, meaningful film-making – cue a swooning woman-and-fish song and dance routine straight out of the golden age of Hollywood.

So, will the Academy bite? Perhaps Three Billboards more meets the mood right now for something more raw and real. Personally, I’d argue that Del Toro’s film, though set in 1962, is as timely and relevant in its portrayal of an invisible woman taking matters into her own hands. (Elisa is repeatedly ignored and dismissed as a lowly “piss-wiper”.) And unlike the heroines in the monster movies Del Toro grew up watching, she doesn’t need to be rescued from the clutches of a monster; she is doing the rescuing.

Some, I know, have found The Shape of Water’s heart-on-sleeve sincerity a bit dippily naive or indulgent. But its message of kindness and acceptance left a lump in my throat – and ought to leave some statuettes on Guillermo del Toro’s mantelpiece, too.

• This article was amended on 1 March 2018 because The Shape of Water is set in 1962, not 1963 as an earlier version said.

