PHOTO COURTESY UNIVERSAL PICTURES

What if there were a pool that was … you know, scary?

That seems to be all the idea needed for Blumhouse Productions to make “Night Swim.” The horror mega-studio, which never met a spooky idea it didn’t finance, frequently turns a half-baked idea into gold.

Unfortunately, “Night Swim” isn’t even half-baked.

The premise, teased in an opening flashback and fleshed out (kinda) in the last reel: A suburban backyard swimming pool, fed by a mysterious underground aquifer, gives swimmers terrifying visions. If they keep wading long enough, they go mad, disappear or both.

How was this problem not resolved via concrete after the first missing person? I have no idea.

Ray Waller (Wyatt Russell), a former baseball player struggling with medical problems, moves his family into the house adjoining the spooky pool. Everyone but him — wife Eve (Kerry Condon, who really should have better things to do), daughter Izzy (Amélie Hoeferle) and son Elliot (Gavin Warren) — immediately sees one or more scary whatsit while swimming. Meanwhile, his health problems clear up. (The pool is selectively terrifying, apparently.)

When Ray’s behavior becomes erratic and the children nearly drown more than once, Eve begins to question whether or not there’s more in the pool than a few hundred gallons of water. She’ll dip into a cliched search for answers before ultimately just brawling with the pool monsters.

Early on, there’s a hint of something more significant in “Night Swim,” even a smattering of commentary. Ray’s descent into despair — represented by shadowy shots of trophies gathering dust in the garage — quite nearly makes an argument about the way comfortable, suburban living grinds away at our ambitions and dreams.

Then, instead, creepy monsters grab at wading legs. The fact that writer/director Bryce McGuire nearly wove a compelling tale doesn’t redeem “Night Swim.” In fact, the missed opportunity makes its lazy conclusion even more frustrating.

My Rating: 4/10

“Night Swim” is now playing in theaters.