It’s a better than even bet that when the tormented protagonist of a story is the owner of a charter boat called Serenity, the name has some deep meaning in the writer’s mind. That’s certainly the case with Steven Knight’s film, which proves to be an extremely silly treatment of a very serious subject, and an irritating puzzle to boot.

Matthew McConaughey plays Baker Dill, a seen-better-days veteran living on Plymouth Island, eking out a living by taking vacationers out to catch sharks and tuna. His first mate Duke (Djimon Hounsou) is concerned about what might be called his boss’ Captain Ahab complex—an obsession with catching a particularly large tuna he’s named Justice. Dill lives in a shack perched atop a cliff near a lighthouse, and everybody he interacts with—the bartender at the local watering hole, the owner of the bait-and-tackle shop, even Connie (Diane Lane), the woman he occasionally sleeps with and whose cat she’s always asking him to find—is kind of peculiar. In fact, there’s something a bit off about the whole place.

Dill’s curiously repetitive existence is suddenly made more frazzled by the appearance of some unexpected visitors. One is Reid Miller (Jeremy Strong), an oddball representative from an equipment company who offers him a free trial of a new fish-finding gizmo. The other is his ex-wife Karen (Anne Hathaway), a slinky femme fatale who asks him to murder her new husband Frank (Jason Clarke), a rich brute who abuses not only her but Baker’s son Patrick (Rafael Sayegh), an introvert who spends all his time on the computer playing intricate video games. She’s persuaded Frank to go out on Dill’s boat to catch a trophy fish, and wants him not to come back from the trip.

It seems initially that “Serenity” is nothing more than a weirdly stylized tuna noir, but as it proceeds the movie grows increasingly strange, with Dill beginning to suspect that he might be in some waterlogged version of the Truman Show. Of course, it might just be that he’s going bonkers; certainly Duke and some of the other islanders think he needs a doctor. One doesn’t want to spoil the movie for anybody intrigued by its premise and wanting to unpack its mysteries by revealing its secrets, but perhaps a hint is permissible. Do you remember the old NBC series “St. Elsewhere”? Do you recall its controversial ending? Knight apparently does, and when you get into the last act of his film and realize where it’s headed, you might just want to be elsewhere, too.

Anyway, those who choose to venture out on Knight’s voyage can expect some pleasures. The visuals are nice, with the location nicely captured in Jess Hall’s widescreen cinematography. And Benjamin Wallfisch’s score has some impressive moments. You also have to admire the effort Laura Jennings’ editing exerts to be honest about what’s happening through quick montages, even if their surrealistic blur can be annoying.

There’s far less to appreciate in the acting. McConaughey certainly invests Dill with lots of intensity, but much of what he does has a histrionic vacuity to it; it comes across as effortful pose. Hathaway slinks about in her revealing dresses and trenchcoat, but instead of steaminess what results is more mannequin than actress; and Clarke’s personification of sheer nastiness has no shading whatever. Neither does Strong’s bureaucratic nerd, a part that once might have been written especially for Anthony Perkins.

And yet the fault doesn’t really lie with the actors; it rests in Knight’s conception of the characters they are playing—all pawns in what turns out to be an elaborate charade, the explanation for which will probably infuriate most viewers.

Of course, there are some people who enjoy McConaughey’s Lincoln commercials, so there may be a few who will take to “Serenity,” too.