Take Bait, for example, or Sharknado. Terrible films, but films you could happily watch and enjoy because they were bad.
In the case of Sharknado, obviously, that was the point. With Bait, less so - and yet still I'd happily watch it again.
Then there's 47 Metres Down.
A film so bad, it's terrible.
Where do you start with something like this?
You know it's going to be terrible when in the opening scene the camera follows Vampire Diaries star Claire Holt through a swimming pool, focused largely through her legs.
This is followed by Mandy Moore (remember her?) being upended into said pool, spilling her red drink into the water.
For some reason she appears to be drinking blood, seeing as nothing else reacts like that when hitting water...
Then the dialogue kicks in.
And you realise it was scripted in a hurry by someone who has never heard humans speak before and is writing with a crayon.
A large, blunt crayon.
Because they're not allowed near sharp objects.
And then things go really down hill.
A text conversation with a boyfriend belongs in a whole other movie, the sexual politics belong in a whole other decade and the bit where Moore worries about how big her ass looks in a wetsuit belongs in the bin.
Then, we get to go in the water.
I'd suggest at this point that you try and work out who sails the boat away given everyone on board got out, but don't bother.
You really won't care.
Everything we've had to endure up to this point is leading us to the real drama. The tension. The horror, if you will.
Which isn't technically true - the horror doesn't come from what happens in the water, the horror is the whole sodding movie.
You'll notice at this point we haven't really summarised the plot - don't worry, you haven't missed anything.
Everything so far has led us to the point they get into a dodgy looking rusty cage, which is lowered into the ocean on a winch which has seen better days using worn string.
Then, shock and horror and OMGs abound, THINGS GO A BIT WRONG.
Sadly, not fatally, so we have to endure these two numpties attempting to act scared while under water.
The attempts to fashion tension and drama are beyond laughable - to the point that, when an underwater flare is ignited, the three sharks we suddenly see are less lifelike than the Jaws model at Universal Studios.
And I still have no idea where the third one came from.
Did I mention the bit where Ms Moore gets a sense of impending doom and a case of the heebie-jeebies from simply staring at a wooden post with a shark painted on it?
It's exactly that kind of film.
Only it is taking itself very seriously.
And don't get me started on how someone who admits to having NEVER dived before is able to change air tanks under water...
OK, yes, there was one - ONE - scene where we jumped slightly, but if 47 Metres Down had any sense of fun or mischief then it could almost be OK.
Instead, we have scenes of meaningful dialogue horrendously over-dubbed while our two stars walk along a beach towards the doom-laded bit of wood mentioned above.
The only thing worse than watching this film was the realisation that we were in a screening where people had willingly paid money to see it.