For those few cinema scholars who speak of some motion pictures as “films,” and others as “movies,” Guillermo del Toro’s glorious “The Shape of Water” refuses to go tidily into either box. A ravishing, eccentric auteur’s imagining, spilling artistry, empathy and sensuality from every open pore, it also offers more straight-up movie for your money than just about any Hollywood studio offering this year. This decidedly adult fairytale, about a forlorn, mute cleaning lady and the uncanny merman who save each other’s lives in very different ways, careers wildly from mad-scientist B-movie to heart-thumping Cold War noir to ecstatic, wings-on-heels musical, keeping an unexpectedly classical love story afloat with every dizzy genre turn. Lit from within by a heart-clutching silent star turn from Sally Hawkins, lent dialogue by one of Alexandre Desplat’s most abundantly swirling scores, this is incontestably del Toro’s most rewarding, richly realized film — or movie, for that matter — since 2006’s “Pan’s Labyrinth.”

With encouragement from critics and awards voters, discerning viewers should make Fox Searchlight’s December release the season’s classiest date movie — for perhaps the greatest of “The Shape of Water’s” many surprises is how extravagantly romantic it is, driven throughout by an all-conquering belief in soulmates as lifelines. This is del Toro’s second straight film to smuggle a swooning, lovestruck heart beneath pulpier genre clothing (“It’s really a Gothic romance” became something of a fan meme in response to 2015’s horror-styled “Crimson Peak”), though this time, there’s nothing arch about its romanticism: It’s as pure-hearted and simple a girl-meets-Amazonian-water-creature-who-might-just-be-a-god story as any ever made.

The film announces its fairytale intentions from the outset, via the florid, characteristically comforting Richard Jenkins voiceover that bookends proceedings: References are made to “the last days of a fair prince’s reign,” “the princess without voice” and “the monster who tried to end it all,” as the shabby contents of an ocean-flooded Baltimore apartment float in the blue like sea anemones. It’s a dreamy image on which to kick off a story that never seems entirely of this world, even as we’re introduced to the mundane everyday routine of Elisa (Hawkins), voiceless and orphaned from infancy, who scrapes together a living as a cleaner in a top-secret government laboratory, where assorted shady experiments are conducted in a fevered spirit of anti-Russian paranoia. The year, of course, is 1962.

Elisa is lonely, but she’s not alone; indeed, loneliness is a condition common to most of the film’s characters, from her ceaselessly chatty workplace pal and protector Zelda (an irresistible Octavia Spencer), who carps despairingly about her unresponsive husband, or her avuncular neighbor Giles (Jenkins), a repressed gay illustrator who can’t find an outlet for either his work or his persecuted affections. No one, however, is more desperately isolated than our nameless creature of the deep, dragged from South America to a murky tank at the lab by scientists convinced his supernatural capabilities can give America an edge in the space race. (If you’re wondering why, the film has no answer: Cold War bureaucrats are not presented here as the epitome of rationality.)

Yet when Elisa encounters him through the glass on her cleaning rounds, she sees not a scaled, finned, algae-colored beast, but a kindred spirit, one who shares not just her silence, but her misfit perspective, her scars of abuse and her ebullient love of Benny Goodman records. Music is the chief conduit of feeling throughout “The Shape of Water,” whether in the form of Desplat’s ornate, orchestral jazz compositions, or crackling vintage cuts from the screen musicals Elisa and Giles consume together. Harry Warren and Mack Gordon’s wistful “You’ll Never Know” may have won an Oscar in 1943 for the lightweight Alice Faye musical “Hello, Frisco Hello” — briefly glimpsed on a boxy TV screen — but del Toro’s film has just given it a new, definitive cinematic context, as the recurring leitmotif for Elisa’s inner torment.

Credit the marvelous Hawkins, her fine-featured but robustly expressive face in constant emotional motion, for making us believe as swiftly and as easily as we do that Elisa and the creature are made for each other. (He, meanwhile, is given agile form by a dazzlingly prostheticized Doug Jones, del Toro’s regular collaborator.) It’s an empathetic leap without which the breathless plotting that ensues simply wouldn’t fly, as Elisa and her allies embark on a fearsomely tricky scheme to free her scaly beloved, with Michael Shannon’s cruel, sharp, literally gangrenous federal agent as their enemy-in-chief. Never one to only lightly squeeze an especially juicy character, Shannon gives “The Shape of Water” a villain to relish: bullish in stance but lizardy in body language, spouting the rhetoric of a government more interested in killing what they don’t recognize than exploring unknown quantities. “We don’t need to learn,” his military superior barks; del Toro and Vanessa Taylor’s lively, limber script does not wear its liberal anti-establishment credo lightly.

Even once the narrative wheels are roaringly in motion — with del Toro and editor Sidney Wolinsky jangling through a handful of sharply sustained tension setpieces — “The Shape of Water” finds time for arresting interludes of off-kilter poetry. For a film that could easily have been refashioned as a family-friendly adventure, the film takes a bracingly candid, mature approach to sexuality, giving Elisa a vigorous carnal identity that belies the character’s more ethereal aspects. There’s real life filed between the film’s most heightened flights of fairytale fancy: Spencer and the wonderfully crumpled Jenkins, in particular, bring gently hardened everyman texture to the table every time matters threaten to take a turn for the twee.

It’s that essential foundation of human credibility, however outlandish the overlying circumstances, that gives del Toro license to crank up the aesthetic stylization to eye-popping degrees. Dan Laustsen’s athletic, kinetic lensing skips dizzily between lighting schemes and color palettes from assorted eras and classes of vintage Hollywood — at one critical point surging into purest, loveliest monochrome — while seamlessly integrating his director’s state-of-the-art visual effects into this old-school stew. Paul D. Austerberry’s production design is a singular triumph, its every interior surface painted in mossy greens, soiled browns and gutsy crimsons that all appear sodden to the touch, as if the creature’s watery spiritual home might crash the walls at any minute.

Del Toro’s wide-eyed cineaste fixation, meanwhile, is present in the finest technical details, with echoes of “The Red Shoes” in the design of Elisa’s apartment — itself situated above a struggling picture palace, where hoary Biblical epics play to a near-empty auditorium, the audiences kept home by their television sets. Desperate for custom, the theater proprietor offers Elisa free tickets, forecasting the end of it all: a winking nod to present-day prognoses of the Netflix-induced death of cinema. As long as filmmakers like Guillermo del Toro are producing movies as strangely, rapturously alive as “The Shape of Water,” those remain pretty empty threats.