I read the synopsis and i thought this was gonna be dumb as hell, so i watched it just for fun. As it progresses, there are some twists and turns that made it more interesting than it seems at first. Make no mistake, it's maybe less dumb as it seems but it's still ridiculous and non realistic. These twists are totally unconcincing and at some point, it felt like a comedy, more unintentional than intentional. But it was still kinda interesting and for a "dude falls into a manhole" movie, it's surprisingly not boring at all. Things keep happening and at times, it's enjoyable.
So, if you lower your expectations and suspend your brain function, there is a chance you'll enjoy this, especially if you like "one location" thriller movies. Of course, i can't recommend it to anyone, there are thousands of better movies to watch.