“Rotting in the Sun” is the most sexually explicit gay missing person hunt in the history of cinema.

It’s a dark, deadpan comedy that isn’t really funny, but whose premise is the the quintessence of “permission to laugh.”

A suicidal filmmaker desperate for a comeback or a quick, painless death, goes missing in Mexico City. And the only person concerned about what might have happened to him is this vapid American Instagram influencer who desperately wanted to A) team up with him on a project and B) get in his pants, although they meet on a Mexican same-sex vacation mecca that’s basically one long nude bacchanal.

Pants? Optional. Frowned upon.

An added twist is that the missing filmmaker is the this film’s director and co-writer, Chilean Sebastián Silva (“The Maid (La nana),” “Crystal Fairy & the Magical Cactus”) playing a thoroughly unlikable exaggeration of himself.

The influencer is comic Jordan Firstman, who had an Instagram moment during the pandemic. Firstman’s parody-version-of-himself is a relentlessly upbeat hedonist without a deep thought in his head or a sexual inhibition in his over-exposed body.

They meet, by accident and by coincidence, in the waters off Playa Zicatela. Jordan’s a guy who is drowning, yanked along by the rip tide while a vast audience of nude gay men shout at him from the beach, that someone should save him, and who shout directions at Sebastian, already in the water, to do what they won’t.

But Sebastian is a brooding ketamine addict, buried in reading and (voice over) quoting E. M. Cioran’s “The Trouble with Being Born” and who has come to this beach to either talk himself out of suicide, or do something about it.

Jordan, not really “saved” by Seba, bowls him over with fanboyish enthusiasm for his work, happily crediting Sebastian with his salvation and ready, on the spot, to pitch this inane “‘Curb Your Enthusiasm,’ but positive” show concept — “You Are Me” — to the filmmaker, who isn’t having it.

“You’re not funny at all,” is Sebastian’s opening salvo. But Jordan’s relentless invitations, come hithers and the like wear on him. At least he doesn’t end it all on vacation, although Jordan videos Sebastian snorting Ketamine and posts it on Instagram. “That’s what I do,” the empty-headed icon bubbles.

When Sebastian is sober and focused enough to have his Zoom pitch meeting with HBO, the only show idea they go for is “You Are Me,” a plot point ripped off from “Seinfeld” and plenty of other showbiz stories.

But when Jordan shows up at Sebastian’s arist’s studio/apartment, the guy is nowhere to be found. Seba’s “friend,” who owns the building, isn’t concerned. His maid (Catalina Saavedra, who starred in Silva’s breakout film, “The Maid”) is evasive, using the language barrier to avoid the annoying gay gringo.

Can this hedonistic dim bulb ever sober up enough and get his mind off sex long enough to Google Translate his way to figuring out what happened to this filmmaker, whom he’s calling “My husband” on social media?

Director of photography Gabriel Díaz uses a lot of hand-held sequences to accentuate the social media vibe of this story, which is basically a “Columbo” episode for the influencer era. We know what’s happened. We’re just wondering if the shallowest American south of the border can figure it out.

The tale, acted-out in Spanish and English, unfolds ever-so-slowly. Truth be told, the Anal Sex Beach Party goes on and on as if to test the audience, and revisiting that carnal chaos for a “party” Jordan throws in his missing “husband’s” flat just underscores how out of his TV friendly twink is, picking up clues and “lighting up” Sebastian on social media for the perceived slight of “ghosting me.”

Silva manages little suspense, and the slack pacing and odd “Why would he/she do that?” moment had me on the fence with this one.

But a bravura finish seals the deal. So if you watch only one sexually-explict gay sex romp/missing person mystery this year…

Rating: unrated, drug abuse, suicide is discussed at length, explicit sex, full frontal nudity, profanity

Cast: Sebastián Silva, Jordan Firstman, Catalina Saavedra

Credits: Directed by Sebastián Silva, scripted by Pedro Peirano and Sebastián Silva. A Mubi release.

Running time: 1:51