Perhaps it was the effects of a bright-blue "sharktastic" cocktail, but about halfway through "Meg 2: The Trench," this self-serious sequel suddenly becomes funny. The moment arrives when DJ (Page Kennedy), a mouthy techie who survived the first movie, tells Mac (Cliff Curtis) that this time, he has poison-tipped bullets, "just like in Jaws 2." Finally, we breathe a sigh of relief: The movie is in on the joke. Now we can laugh with "Meg 2: The Trench," rather than at it.

But it's not until we're out of the trench and up on the surface that director Ben Wheatley loosens up a lot, and has a little fun.

That first half is dire straits. Wheatley takes the helm from Jon Turteltaub, who directed the delightfully ridiculous original giant shark movie "The Meg" in 2018, and works from a script by original writers Jon and Erich Hoeber and Dean Georgaris.

The film's focus is on shark hero Jonas (Jason Statham), and the teen in his care, Meiying (Shuya Sophia Cai), the daughter of scientist Suyin, who featured in the first film and is now mysteriously dead. Suyin has been replaced by her brother, Jiuming, played by Wu Jing, one of China's biggest action stars.

Jiuming is a daredevil marine biologist who has taken up his sister's mission to protect the oceans through underwater exploration, and he's also taken a special interest in training and befriending Haiqi, the young megalodon living in the care of the Oceanic Institute.

As explorers are wont to do, they poke around down in the trench, and what do they find? Capitalism! Because there isn't an inch on this planet that some craven rich person won't figure out how to strip-mine. The secret mining operation serves as the plot wrinkle to throw our leads into danger.

The whole gang heads to "Fun Island." On the beach, all manner of ancient sea creatures terrorize clueless tourists, as they are wont to do, and Wheatley lets it rip, taking the opportunity to riff on "Jaws" and other classic creature features like "Predator" and "Jurassic Park."

It's an odd viewing experience, to have the second half of a movie, not necessarily redeem the bland first half, but rather, find its sea legs, leaning into the slippery silliness of a summer shark flick.

'Meg 2: The Trench'

2½ stars out of 4

Rated: PG-13 for action/violence, bloody images, language and brief suggestive material.

Where: In theaters Friday.