The current run of DC comic-book movies is peacing out, and before saying goodbye, it’s leaving us with Jason Momoa getting wet on by a baby as well as an octopus riding a seahorse. So, thanks?

Momoa’s big lug who talks to fish has one action-packed quest left in him with the sequel “Aquaman and the Lost Kingdom.” Director James Wan’s new Atlantean adventure (★★½ out of four; rated PG-13; in theaters Friday) releases at a time of transition, when superhero films have lost some of their luster and a rebooted DC cinematic universe – headed by James Gunn and Peter Safran – arrives in 2025. But the movie neither sinks nor swims: It’s aggressively fine, floating along as a breezy enough outing – and a brotherly one – without any particularly spectacular strokes.

Since his last solo film in 2018, Justice Leaguer (and king of Atlantis) Arthur Curry (Momoa) has also added husband and dad to his resume. Yet he’s struggling to get his bearings: He’s devoted to infant Arthur Jr., though has a hard time balancing his parental and royal responsibilities. Alongside his wife Mera (Amber Heard), Aquaman is bored dealing with political councils and feels like he’s not cut out for this high-profile king gig.

He just needs somebody to punch really hard. Old foe Black Manta (Yahya Abdul-Mateen II) returns with revenge in his heart, obsessed with finding Atlantis, burning down the place and killing all of Aquaman’s loved ones. The supervillain finds a magical artifact from Atlantean lore called the Black Trident and becomes possessed by an ancient evil.

Manta launches a massive strike against Aquaman’s people, causes climate-related chaos and eventually targets Arthur and Mera’s little one. Aquaman needs help from someone who knows Manta well, so the hero busts his nemesis, half-brother and former king Orm (Patrick Wilson), out of prison. Together, the best frenemies go on a mission that takes them to the mythical lost kingdom of Necrus and along the way try not to kill each other.

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Wan, a master of horror when not doing superhero movies, tosses in a lot of cool B-movie creatures, nifty underwater sights and some seriously dark visuals (including aqua-zombies!), so much so one has to wonder how good these “Aquaman” movies would have been had he gone all in on the strange and unusual. “Lost Kingdom” also boasts a healthy sense of humor – the best part of the movie is Arthur and Orm doing their own version of “Step Brothers,” evolving from bickering bros to oddball besties. Yet that enjoyable vibe is continuously undone by an overpowering earnestness.

Black Manta looks better than ever, the scars starting to mount as his super suit gets higher tech, though Abdul-Mateen’s baddie is more one-note this time around. Nicole Kidman and Temuera Morrison return as well, playing Aquaman’s mom Atlanna and dad Tom, and Dolph Lundgren earns a bigger supporting role as Mera’s dad Nereus. As for the more unconventional characters, just as Julie Andrews voiced a sea monster in the first “Aquaman,” Martin Short is in the new film as casino boss Kingfish. (John Rhys-Davies also gets more to do as crabby dude Brine King.)

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Momoa’s larger-than-life personality powers these films, making what could easily be a vanilla character a brash and bold delight. With larger changes afoot, “Lost Kingdom” does seem to be his swan song before someone new like, say, Warner Bros. favorite Timothée Chalamet takes over the character. (If the studio wants to print money, they’d gin up a “Justice League” with Robert Pattinson’s Batman and Margot Robbie’s Harley Quinn partnered with Aqua-Timmy and Taylor Swift as Wonder Woman. With Greta Gerwig directing, natch.)

This take on Aquaman at least gets a mic-drop moment, fleeting as it may be. Even with “Migration” also opening this holiday weekend with a bird-brained family on the loose, “Lost Kingdom” is the biggest lame duck of them all.