Deep in the Mariana Trench a humungous prehistoric mega-shark is minding its own business. Naval Captain Jonas Taylor (aka Jason Statham) interrupts its day with a brightly lit diving unit which practically says ‘eat me’. Not all his crew get away and Taylor sinks into a boozy retirement, full of regret. Five years later, another crew is about to become tinned food for the 70-foot beastie. And this time it’s his ex who’s in trouble. But the rescue goes awry when the megalodon follows them up into the Pacific Ocean. And this time a whole coastline of Chinese food is on the menu.

If you’ve seen the trailer for The Meg, you’ve seen a better film. Snappily edited, a massive fishy shadow swims under a boat, a little dog yelps as it spies a fin the size of a yacht. ‘Chomp on this’ says the trailer. It’s fun, knowing, and promises a breezy blockbuster. Playfully riffing on Jaws, Jurassic Park and every other mainstream monster movie, it says ‘yep, we’re not one of those’, perfectly content to be a pastiche.

Sadly, though, The Meg doesn’t live up to its own wink-wink billing. Neither as funny as the trailer nor as tense as the movies the trailer sends up, it doesn’t know who to please. A slow Jurassic-like start culminates in a genuinely nervy initial descent, Statham not believed by his crew or his bosses that he saw a massive sea beast. Branded a nut or a coward for leaving some of his crew members behind to save the rest, it plays like a drama. True to Jaws, the creature’s not fully seen for a long time. So far so serious.

In Jaws the creature’s surfing in our waters seeking whom he may devour. He is, as such, an enemy and you root for the reluctant hunters. Here you feel sorry for the fish, even a CGI one. And that’s not good for a monster movie. At least in King Kong and the recent Jurassic World: Fallen Kingdom it’s evil people who bring Kong and the dinos onto our soil. With The Meg it’s a mish-mash of good guys and money men that do it. So, of course, you root for the bankers to get bitten and for the pooch and Chinese sunbathers to survive. But it’s hard to cheer for Statham’s ‘cruise-aid’ to send the beast to the bottom.

On the plus side, Statham is excellent. As an actor and as a diver. The latter not surprising as the young Stath competed for England as a diver in the 1990 Commonwealth Games. In The Meg he carries the movie, convincing as the haunted hero and handy with the infrequent quips. With no martial arts to perform, his physicality still makes you believe a man can out-swim a mega-shark. And his sparky relationship with the film’s imperilled kid, Meiying, (a winning turn from Shuya Sophia Cai) is at the heart of it.

Boats are smashed to smithereens and helicopters are simply flying fish-food. The set pieces are sound but not stupendous and the CGI works well, even if the megalodon seems to change size depending on the angle from which you see it. The Meg isn’t as off-the-wall silly as Sharknado or as sci-fi serious - or scary - as Deep Blue Sea. But in aiming for a family audience it isn’t really anything at all.

‘Chomp on this’ for sure. But it’s neither fast food nor haute cuisine – so remember to take your own salt and vinegar.

The Meg is a prime example of how a great concept (Jason Statham vs. a giant prehistoric shark) and a killer marketing campaign (how can you not love this poster? Or this one?) can marry together and elevate a pretty good film into an end-of-summer blockbuster triumph.

The film opens with Statham's Jonas Taylor in the midst of a deep sea rescue mission. His craft ends up attacked by an unseen threat, forcing our hero to abandon two of his crew members. This leaves him disgraced, divorced, and publicly rejected for his assertion that a creature attacked them. Five years later, and it looks like he will be proven right by the arrival of a giant prehistoric shark, discovered by a research crew whom he has now been roped into rescuing. From there, Jonas must battle the monster across the sea, preventing it from killing more people.

The Meg is essentially three segments clumsily stapled together. The first is all claustrophobic spaces, clunky exposition and deep sea exploration. The second follows the giant beasty out into the open sea, and is marked by awkward banter, with our motley crew and Jason Statham having a series of near-misses with the titular threat. Then the third, and certainly most enjoyable, part reaches the beach, giving the film the premise it has been sold on: a giant shark chowing down on obnoxious tourists. Certainly The Meg is no Jaws, lacking the craft to make the narrative and setting changes feel organic. Yet this doesn't prevent the film from being a consistently enjoyable one.

Part of the appeal has to be in the casting of Jason Statham in the lead role. The film seems to fit perfectly both with his well-practised gruff cinematic persona and his previous life as a professional diver. The rest of the cast are all fine, with some effective work from Bingbing Li and Ruby Rose. And Shuya Sophia Cai as the seemingly necessary (for these kind of films) child along for the ride is on the right side of precocious. Jon Turteltaub directs competently, managing to show off the shark's huge mass. I particularly liked the shots of the Meg swimming beneath unsuspecting tourists. Certainly this film isn't going to win awards for craft, but it is a proficiently put together B-movie.

There isn't really much more to say on The Meg. You'll either be sold on the film's central concept, or you won't be. The film lives up to it, never exceeding it and becoming a great shark thriller (such as The Shallows), nor does it besmirch the whole endeavour. This is the kind of film that delivers the dumb fun that many will be seeking at this time of year.