Private islands are never all they’re cracked up to be.

At the movies, that is.

A group of 20th century settlers find out the hard way in director Ron Howard’s survival drama “Eden,” a loony soap opera in the sand that premiered Saturday night at the Toronto International Film Festival.

Based on an unbelievable true story, the braving-the-elements flick is what you’d imagine a 1929 season of “Survivor” might look like.

Sydney Sweeney is part of the starry cast of Ron Howard’s survival drama “Eden.” AP

Humanity is at its bestial worst as residents forge alliances, swap sex partners for others, shoo wild pigs and confront monstrous villains. Ultimately, there’s a winner. A sole survivor, if you will.

Howard and screenwriter Noah Pink let loose telling the trashy tale of Floreana, a then-uninhabited island in the Galapagos.

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The first arrivals are a German couple, Dr. Friedrich Ritter (Jude Law) and his wife Dora (Vanessa Kirby), whose Swiss Family Robinson-style exploits become the talk of Europe when his letters are published by newspapers.

Inspired by their adventurous pluck and looking to escape the rising tide of Fascism are Heinz Wittmer (Daniel Brühl), young bride Margaret (Sydney Sweeney) and their son Harry (Jonathan Tittel). They’re a chilly bunch, even for Germans.

When the Wittmers reach land, they are distraught to discover that it’s not a Club Med. There is no discotheque, but there are just two fresh water springs and terrain that’s tough to farm.

But with American Gothic stoicism, they get to work building a shelter and a new life — only with no help from the philosophy-spewing Ritters who resent the newbies’ incursion.

Howard’s film takes place on a remote island in the Galapagos. Courtesy of TIFF

Too bad there are more intruders to come. 

The Wittmers are followed by Eloise Bosquet de Wagner Wehrhorn (Ana de Armas), a high-on-her-own-supply baroness with the glazed look of a serial killer. She’s accompanied by two gents, Rudy (Felix Kammerer, the wonderful star of “All Quiet On The Western Front,” who must be in more major films) and Robert (Toby Wallace). She sleeps with both — at full volume.

Evil Eloise, who makes Goldfinger look calm and circumspect, wants to build a grand hotel called the Hacienda Paradiso, which has a Fyre Festival ring to it from the off.

Ana de Armas plays Eloise, a villainous baroness with many sinister secrets. AP

Everybody hates everybody. They steal food, envy each others’ homes and, on occasion, threaten their neighbors’ lives. The stakes rise even higher when a baby is born and a Hollywood filmmaker rolls in.

All of this madness actually went down, only, I’d imagine, with slightly less clunky dialogue.

When oil magnate and film producer George Allan Hancock arrives, Eloise asks him, “You live in Hollywood?”

Replies Hancock: “I own Hollywood.” What a verbal anvil.

“Eden” is never less than juicy, though, and made all the more so by its A-list cast rolling around in the mud while looking implausibly ravishing.

Vanessa Kirby’s character Dora is married to Dr. Friedrich Ritter (Jude Law). AP

As big as these actors’ personalities are, their differences ratchet up the animosity. De Armas’ baroness stands for extravagant gluttony, which peeves Law and Kirby (who always appears to be in a trance), who are thoughtful and free-spirited academics. Law’s doc is a sneering jackass, which the actor excels at.

Sweeney goes most against type — from “Euphoria” and rom-coms to full hausfrau. The actress is compelling and has a birthing scene so wild that Shonda Rhimes would tip her hat.

De Armas’ character, while a total whack- job on paper, needed to be humanized a tad more. She has one sweet, fleeting interaction with Harry and then goes right back to being the Wicked Witch of the Eastern Pacific.

She’s still a hoot. And Howard has made his most enjoyable and creatively successful movie since, gosh, “Frost/Nixon”? He’s not back to his 1990s and aughts peak — there is an undeniable layer of tawdriness to “Eden” — but it’s refreshing to see him take a load off and not be so serious.

This hellish island’s done him a world of good.