PHOTO COURTESY WARNER BROS. PICTURES

What do you get when you try to make a dumb, fun movie — but forget to make it fun?

Dumb. You get dumb.

“Meg 2: The Trench,” a case of diminished returns from the already lukewarm “The Meg,” manages to make three giant, angry sharks uninteresting. Relatively little time is spent with the prehistoric fish; most of our experience is focused on half-hearted action sequences near, but not actually involving, any aquatic megafauna.

Maybe they needed to save money and could only afford so many shark shots? Let’s see … no, they spent $129 million to make this thing. Inflation must have hit the green-screen industry pretty hard.

Ecologically minded billionaire Jiuming (Wu Jing) is working on deep-sea research in the Mariana Trench, poking around unexplored depths and attempting to train his pet megalodon. Meanwhile, hard-punching do-gooder Jonas (Jason Statham) is generally helping out and glowering. When the crew — including Jonas’ precocious stepdaughter, Meiying (Sophia Cai) — discovers an illegal deep-sea mining operation, chaos ensues and a trio of angry monster sharks head for the surface.

They also unleash a giant octopus, which does admittedly spice things up a bit. Also … some dinosaurs? Listen, if you’re thinking in there, you’re going to have a rough time.

Every sequence in “Meg 2” has been done better elsewhere; the action is limp and the effects are soupy. Even when we get around to the promised shark mayhem — all of which appears in the film’s trailer, by the way — it looks like meaningless digital foam, as the PG-13 limitations allow for little more than a chomp and a splash.

Statham, always better as part of a team, can’t shoulder such an awkward burden all by himself, and he gets no help from the rest of the cast. Despite deploying every script cliche known to man, “Meg 2” never comes close to grabbing attention — let alone interest.

My Rating: 3/10

“Meg 2: The Trench” is now playing in theaters.