In rebooting the old TV series about lifeguards on a California beach, screenwriters Damian Shannon and Mark Swift and director Seth Gordon have toned down, though not completely expunged, its tendency to leer over slow-mo shots of pretty women in swimsuits, deciding instead to blend a raunchy R-rated comedy of the Judd Apatow/Seth Rogen variety (lots and lots of dick jokes—some grotesquely protracted) with a high-octane action movie (plenty of fights and explosions—many of them crudely prolonged, too).

The result is a hybrid that doesn’t trash a “classic” campy program to quite the extent that the recent “CHIPS,” for example, did, but it doesn’t have the savvy—or the casting chemistry—of a “21 Jump Street” either. This rejuvenated “Baywatch” falls uncomfortably in the mediocre middle, a would-be summer blockbuster that might not be as excruciatingly bad as you might fear but certainly isn’t a cinematic day at the beach—unless it’s one where guys are constantly kicking sand in your face and dropping their trunks for shock effect while scantily-clad girls act as beyond-the-reach eye candy.

Dwayne Johnson plays Mitch Buchannon, the muscular leader of the lifeguard team who sees it as his duty not only to save peoples’ lives—which he does, aided by his ultra-competent second-in-command Stephanie Holden (Ilfenesh Hadera) with the same sort of gung-ho machismo the actor exhibited in fare like “San Andreas”—but to keep the beach free of crime, even though his frustrated boss Captain Thorpe (Rob Huebel) and local cop Sgt. Ellerbee (Yahya Abdul-Mateen) repeatedly tell him that the latter is a police responsibility he shouldn’t take on. But the appearance of drug packets in the sand tells him that some sort of malfeasance is afoot, and he won’t let up until he puts a stop to it.

Mitch is right, of course: sultry Victoria Leeds (Priyanka Chopra), the owner of a glitzy new seaside club, is masterminding a drug-smuggling operation and buying up nearby properties, using force if necessary, to cement her control. Before he can act on his suspicions, however, he must oversee the selection of new trainees for his team. One is inevitable: cocky, selfish Olympic gold medal winner Matt Brody (Zac Efron), who is nonetheless in the doghouse with the public for ruining the American team’s chances in the relay and whom Mitch is being forced to accept for PR reasons. Another is lovely Summer Quinn (Alexandra Daddario), whom Brody will find irresistible.

The third is Ronnie Greenbaum (Jon Bass), an overweight doofus whose infatuation with buxom lifeguard C.J. Parker (Kelly Rohrbach) is so great that just being near her leaves him a blubbering mess. How he could have been chosen despite his manifest ineptitude is obvious: he’s meant to serve whenever needed as an easy comic target—indeed, he’s the focus of the movie’s first boner gag, a long, excruciatingly unfunny bit. For the rest of the move he becomes the human puppy dog to whom the camera will turn for “hilarious” reaction shots—a truly ignominious fate.

From that point the plot is pretty rote. As the crew become more and more involved in working out the specifics of Leeds’ scheme—an effort that includes such sights as Efron winding up in drag as a disguise, and playing with a corpse’s genitals (a sequence as cringe-worthy as the closing bit from “Bad Santa 2”)—Matt gains a sense of responsibility and comes to see Mitch as a big brother (inevitably, the squad becomes a surrogate family). There’s also the obligatory roadblock which removes Mitch temporarily from the team, allowing for his mentor (a predictable cameo by David Hasselhoff) to pop up and remind him of his mission in life. Not to fret: he will reappear in the big Fourth of July finale, in which fireworks of every sort accompany the villainess’ colorful defeat.

Through the mayhem Johnson continues to demonstrate the talent for tongue-in-cheek bravado he’s honed in pictures like “Central Intelligence,” but Efron’s dumb beefcake shtick is getting old; perhaps playing Ted Bundy will get him back on track. In what is essentially a buddy movie for the two, the filmmakers make sporadic effort to provide opportunities for the other cast members to show off on occasion, but the only one who really catches your eye is Bass, and for all the wrong reasons. The guy is apparently meant to be a likable dunce in the Jonah Hill-Josh Gad mold, but he’s annoying from the first moment you see him (in a scene with the underused Hannibal Buress). For aficionados of the old series, and there must be one or two of you out there, be assured that in addition to Hasselhoff, Pamela Anderson shows up, very briefly.

Despite its campiness “Baywatch” is a “prestige” production, shot (in Florida rather than California) in bright widescreen style by cinematographer Eric Steelberg, though as usual nowadays the editing (by Peter S. Eliot) pretty much makes a mess of the chase sequences and the final stand-off, which emerges as borderline incoherent. Christopher Lennertz’s score is instantly forgettable. The whole movie would be too, were it not for the more obnoxious moments that will be difficult to eradicate from your memory.

So goes yet another misfire based on a crummy old TV series. The success rate for this genre is so poor that one might expect even Hollywood studio executives to take notice, but they keep rummaging through the debris of network television for ideas. Here’s a novel notion: try hatching a new one.