The latest attempt by Warner Bros. to expand its fictional superhero universe based on DC Comics comes in the form of “Aquaman,” a film that hits theaters December 21.

Starring Jason Mamoa (pictured above right) as the title character, “Aquaman” is the fifth chapter in the DCEU (DC Extended Universe) and follows the disappointing “Justice League” — a movie plagued by a director swap and a lot of studio interference.

Mamoa previously played the character of Aquaman in last year’s “Justice League” and 2016’s “Batman v Superman: Dawn of Justice.”

Critics and audience members who have seen early screenings of the new flick have given it strong reviews; it’s even well on its way to profitability, thanks to strong international box office numbers.

Plenty of kids and parents are no doubt excited for the movie to make its big splash on American shores. But some should be warned that a movie that examines underwater worlds presents a temptation to Hollywood to preach about climate change that is too great for it to ignore.

“Aquaman” has plenty of climate-change preaching — an element that has weirdly become a staple in action movies in the last decade.

The film’s story involves Mamoa’s Arthur Curry, a man born to a queen from Atlantic, the underwater kingdom; and a Maine lighthouse keeper. The latter is recruited to stop his half-brother, King Orm (Patrick Wilson), who’s actively organizing the seven kingdoms of the sea to declare war on the surface world and the human race.

Why does Orm want to go to war with the land? He explains it plenty of times; it all has to do with wasteful humans overusing their resources and mistreating the Earth.

There’s lots of talk about pollution and littering — there’s even a slideshow of sorts that Orm reveals to his brother, in one of the film’s many soggy exposition scenes.

Though Curry does the right thing and defends the human race against his brother, he does so with little more than a shrug at times. In a scene featuring him and Mera (Amber Heard, above left), an underwater princess, he acknowledges that people in positions of power have no idea what they’re doing — and that people have done plenty wrong.

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It’s a rather cynical piece in what’s supposed to be an inspiring superhero movie.

While points about climate change are not an aggressive driving force in “Aquaman,” they are a central part of the conflict.

People should know going in that there are many people-shaming speeches that will make Al Gore smile from ear to ear.

Check out a trailer for “Aquaman” below: