The Title "Killer Mermaid" really spoils it (in both senses)
"Killer Mermaid" makes it sound like some CGI jump-scare nonsense or semi-parody like "Sharknado"
Whereas it's a more atmospheric film that wouldhave a nice mystery/twist if they hadn't written Killer bloody Mermaid on the Netflix title.
Luckily, I heard it was good a few places or I would never have watched it. So I'm OK. Sadly the inverse is true, that people looking for a more fast paced spectacle or a few laughs are being disappointed by it and giving it bad ratings.
All through the film it seemed obvious it should be called "Mamula" which I see on here it originally was. They then changed it to "Nymph" which was a bit worse before finally ending on the terrible "Kiler Mermaid".
Title gripes aside, as you'll have gathered I really liked it.
It would make a good double-bill with "Dagon"