It’s around the two-thirds mark in “Meg 2: The Trench” that we learn that some of the film’s minor aquatic monsters (not the Megalodons or “Megs” of the title) have developed the ability to walk, and attack, on land. It’s a mistake to bury such a huge twist this late in the movie.

That the human characters aren’t safe on land is a movie in and of itself. Make it the selling point of the third movie. Better yet, make it the selling point of this movie, because nothing about the first two-thirds was working anyway.

Jason Statham is back as diving expert Jonas Taylor. He has some job with an undersea research station, but even within the movie, everyone knows he’s only here to do action-hero stuff.

Working for billionaire Driscoll (Sienna Guillory), Jonas goes on a mission in the titular Mariana Trench with his brother-in-law Jiuming (Wu Jing), possible love interest Rigas (Melissanthi Mahut), some warm bodies not worth your attachment, and just for laughs, his stowaway stepdaughter Meiying (Shuya Sophia Cai).

Watching from the station are returning characters Mac (Cliff Curtis) and DJ (Page Kennedy), as well as new character Jess (Skyler Samuels). When we learn that there’s a saboteur among them, guess who’s catching my gaze.

Megalodons wreck the team’s vessels, so they have to use special suits to walk to a mysterious fully-built facility they’ve stumbled across in the middle of the over-1,500-mile Trench. There’s no getting around it, the underwater scenes in this movie are terrible.

The characters are in thick suits and you can’t tell who’s who, the dialogue is garbled, everything is poorly lit (though these characters make the ridiculous decision to all use their limited light supplies at the same time instead of one person at the front of the group using theirs while the rest follow), and the jump scares are cheap.

I know this movie wants to be brainless fun, but it’s a lot less fun when things are this murky and miserable.

The facility turns out to be the headquarters for an illegal mining operation, with mercenary Montes (Sergo Peris-Mencheta) not wanting our heroes interfering with his boss’s efforts. The characters at the research station aren’t safe from the evil humans either, and for a while this movie just turns into an ocean-based action movie with no Megs in the mix.

Things get temporarily sorted out just in time for the characters to realize that three Megs and a host of other Trench creatures are about to attack the hedonistic human population of Fun Island.

Here’s where “Meg 2: The Trench” has its opportunity to have fun. The Megs and company make snacks out of mercenaries and particularly unlikeable tourists. The heroes use everything at their disposal to stop them, including helicopters, jetskis, Jason Statham being Jason Statham, and of course, lots and lots of explosives.

For roughly the last 30 minutes, the film achieves the “guilty pleasure” status it so desperately wants, too bad it takes an 86-minute slog to get there.

Aside from all the specific, mostly pacing-based issues I have with “Meg 2: The Trench,” my biggest complaint is that the movie generally seems to be aspiring to nothing more than “so bad it’s good” appeal. It’s debatable if it even pulls that tone off well (I say it doesn’t), but there are so many straightforward “good” movies out right now that we don’t need this.

“Barbie” and “Oppenheimer” are both in the middle of historic runs, while the delightful “Teenage Mutant Ninja Turtles: Mutant Mayhem” could use a boost in ticket sales. Don’t divert your time, money, or energy to “Meg 2: The Trench” unless you truly feel that enough resources have gone to movies that are good on purpose.

Grade: C-

“Meg 2: The Trench” is rated PG-13 for action/violence, some bloody images, language, and brief suggestive material. Its running time is 116 minutes.

Contact Bob Garver at rrg251@nyu.edu.