Some questions answered ****spoilers****

Rating: 7/10 (23 December 2018)

This is my opinion. I didn't read the book, but plan to do so. Just want to give my opinion about what some people would call plotholes or impossible happenings.
The creatures - we do get to see them. In the drawings.
What were the creatures' motivation and where did they come from? - a possible explanation was given early in the film by one character - aliens, demons, from another dimension, god, end times. If they were evil, then they caused destruction because its what evil creatures do.
Survivors - Like anything and everything, some people are immune. Now I'm guessing, mentally ill people with distorted thinking simply weren't driven to destruction and saw it as beautiful. Of course whether or not that was the reason for their "immunity", they certainly were highly disturbed afterward.
Getting around - blind people get around everyday. They go to work. Pursue hobbies. Go downtown unaided. Raise kids. Cook meals. Ride public transportation. Put on makeup. I know of a completely blind boy (look it up) who lost his eyes to cancer, who not only played video games, but rode a bike and skateboarded. This kid could go on a walk and correctly identify objects large and small. He had a very, very heightened sense of echolocation. Scientists wanted to study his technique to teach it to others. He's since died when the cancer returned. You can see him on YouTube
So one can't say what's impossible to to unsighted. The character had five years of practice. She was highly motivated and there was at least one scene of her training the children how to listen to determine their whereabouts based on sound.
Kids in the water - Its possible that their tiny bodies were tossed around onto the shore and a rock. Why not?
This is SciFi slash horror film and they always require a suspension of disbelief.