There’s a shark in Paris in a knowingly improbable yet genuinely entertaining summer thriller that deserves its place near the top of a hit-and-miss subgenre.

Almost exactly a decade ago, I unwittingly played into an extremely corny publicity gimmick.

I did this because the film in question was supposedly one of the scariest ever made.

I would wear the monitor, and my involuntary responses would provide everyone with quantifiable proof of just how scary it was.

But it backfired, because the film wasn’t actually very good.

It was a generic found-footage horror called 'As Above, So Below'; the central conceit of which was basically “Aren’t the catacombs scary?” It turns out, they are not.

Or at least that’s what I thought until this week, when a grand corrective entitled 'Under Paris' swept onto the scene.

Now, the central conceit of 'Under Paris' is basically “Aren’t the Paris catacombs scary…” You will be pleased to know the shark helps.

Directed and co-written by Xavier Gens (Lupin, Gangs of London, Hitman), 'Under Paris' is a wildly ambitious, relentlessly silly but genuinely terrifying action-cum-horror-cum-disaster movie about a giant shark that finds itself in Paris.

“But isn’t that impossible?” you’re asking.

“Aren’t sharks saltwater creatures and isn’t the Seine a freshwater river?” You are also asking: “Isn’t the Seine much too cold to comfortably accommodate a shark?” If your grasp of local geography is particularly good, you may also be asking: “Hang on a minute? Isn’t the Seine governed by a complex system of locks? How on Earth would a shark get through those by itself?” The answer to all these questions is: “Shut up, idiot.

” 'Under Paris' knows about all your misgivings, which is why every few minutes it’ll have someone question the logic of the entire premise, only to have someone explain it away with some sort of woolly faux-scientific flimflam.

There are bigger things to worry about.

Like, for instance, the fact that there is a shark in the Seine on the very week that the mayor has organized a triathlon.

It sounds ridiculous, I know.

It sounds a bit like Gens has accidentally made a comedy.

But 'Under Paris' is so fun, and so sturdily built, that you find yourself strapping in and enjoying the ride anyway.

At least before the whole thing explodes (I’ll get to that), there’s a pleasing economy to the film.

It’s slightly reminiscent of 'Jaws', in that the monster gains effectiveness from being hidden a lot of the time.

It’s primarily a human story, albeit a story about a human whose husband is eaten by a shark in the Pacific Ocean and then can’t believe her rotten luck when the same shark effectively follows her home.

It also functions as a pretty nifty parable for the climate crisis.

At first this is explicit – it’s hinted that the shark mutated to allow all the plot holes because it was adapting to the climate crisis – but as it goes along it becomes more and more allegorical.

As the film goes on, all the witless warring humans are so busy chasing their own petty agendas that they fail to notice the unstoppable disaster that has befallen them.

This crescendos magnificently, although it would spoil your fun if I explained it to you.

Of course, 'Under Paris' wouldn’t be a shark movie unless some people got eaten.

And let me assure you that so many people get eaten.

About halfway through the film, when Gens stops playing footsie with us, everything goes completely berserk.

There is one scene in particular that’s like the first bit of 'Saving Private Ryan'.

It’s brutal.

It just never lets up, almost to the point of slapstick.

It’s incredible.

'Under Paris' is a truly great shark movie.

This is an understatement.

It’s one of the best shark movies of all time.

I’m taking 'Under Paris' as proof that you can wildly improve the premise of any horror movie by putting a shark in there somewhere.

After all, it worked for 'As Above, So Below', so let’s keep going.

Let’s have a 'Paranormal Activity' where a shark stands at the foot of someone’s bed and watches them sleep for hours.

Let’s make an 'It Follows' where some poor sap gets chased for the rest of his life in slow motion by a shark.

I haven’t made up my mind about whether 'Rosemary’s Baby' would be better if there was a shark instead of Rosemary or a shark instead of the baby.

Screw it, let’s do both.

It’ll be called 'Shark’s Shark', and it’ll be the scariest goddamn thing you’ve ever seen.