There’s something magical about Guillermo del Toro’s The Shape of Water.

Yes, its premise is founded in fantasy; this love story between a mute woman, Elisa (Sally Hawkins), and a fish man called only “The Asset” (Doug Jones) could be described as E.T. meets Splash, except that that’d imply hijinks and comedy as opposed to espionage, sex, violence and a no-holds-barred commentary on the nastiness of American nationalism.

But it’s not Jones’ aquatic monster that lends the film its magic; it’s the lightness of del Toro’s touch, his ability to take a grand fable and marry its paradoxes. The film is a flamboyant fantasy yet deeply human; old-fashioned yet profoundly modern; filmed with a palate preferring murky, oceanic greens yet somehow bursting with light and life.

I was a sceptic. As much as I admire the craft of del Toro’s films, I find too many of them overly ornate, too satisfied with themselves. The Shape of Water is different; an evolution. It’s undeniably a del Toro film, of course, prone to flights of fancy – whether a luxurious opening shot drifting through an apartment impossibly filled with seawater, or a musical interlude sprung neatly from Elisa’s head – and unapologetic in its debt to fairy tales. There’s a confidence here that I haven’t felt in the director’s work before, though; it’s not that he’s necessarily gotten better at guiding these excursions into his fantasy worlds, but that there’s no longer a hint of shame or uncertainty.

That confidence is shared with a screenplay – from del Toro and co-writer Vanessa Taylor – that exhibits a refreshing reluctance to over-explain. The origins of “The Asset” are implied rather than explicated. The creature’s abilities, its eventual bond with Elisa – we sense their shape but their specifics remain transparent. The antagonist of the piece, a militaristic maniac played by Michael Shannon, offers an explanation for his hatred for the creature in passing but it’s insufficient; we see in his eyes and his very bearing that he despises this thing for its audacity in being something purely original, something impossibly different. That difference is what draws Elisa’s unlikely group of allies – a co-worker (Octavia Spencer), a friend (Richard Jenkins) and a Russian spy (Michael Stuhlbarg) – together, a shared sense of resistance to homogeny that’s unsaid but unmistakable.

I mentioned fairy tales before. If The Shape of Water is a fairy tale, it’s cast from the mould of those ancient fairy tales of gore and grotesquery. A fairy tale of sexuality freed from the strictures of society and the violence that ensues when one challenges the boundaries of that very society. Cheeks are pierced, fingers are severed, fish are fucked; Snow White this ain’t.

All this, this, this.. profanity isn’t an empty attempt to pitch the story to adults. It’s a necessary consequence of a story that’s saying something profound about America’s present from its past. The aesthetic is old-fashioned in an artificial, expressionistic way (I was reminded of The City of Lost Children and the first Bioshock in equal measures). This isn’t accidental; del Toro’s is underlining the futurism of the fifties, an age where America seemed capable of anything yet ended up …here.

Again and again, characters are looking to the future. One rages about photography superseding paintings then raves about a pie franchise. Another buys a Cadillac – painted teal, “the colour of the future” – to solidify his status as a modern man. The Shape of Water offers two visions of the future: a company man, wracked by self-doubt and literally rotting away before us; and a couple silently pirouetting in the sea. It doesn’t preach. It doesn’t tell us which vision to prefer. It doesn’t overreach with its political commentary. It simply presents a picture of pure acceptance and allows us to bask in its beauty.