I had a similar thought; I half expected Krasinski to fart to break the tension with his son when they were at the river.
Anyway, I mostly liked this, but the third act didn’t seem to be as strict with the rules about the monsters and sound, which is a pretty big annoyance when so much tension comes from these strict rules for how the danger works in the first two thirds of the film. Most egregiously, I couldn’t figure out why the monster attacked Krasinski after he took the axe or whatever that was from the shed. That’s a pretty important moment to leave me wondering “wait, why did the monsters suddenly behave that way?”
Smaller annoyances include: how in the world did Krasinski not notice the water pouring into the basement as he was leaving to find the kids? If you spend so much time in silence, you’d absolutely be attuned to any out of the ordinary sound.
And I also didn’t quite understand the layout of the house/farm/basement/other/basement for a while. I didn’t realize that the “lab” basement was in the house and separate from the basement where they lived and kept the baby out in the farm. So thinking that was one location, I was confused about what was down the stairs where the daughter tried to go and Krasinski stopped her. I was waiting for some reveal there, until I finally put together that it was the lab, and then I was just curious in retrospect why Krasinski made such a big deal about it. His reaction to the daughter heading that direction seemed disproportionate for it just being the lab, I expected something more dangerous, and then it undercut the significance I think the movie wanted me to feel when the daughter sees how hard he’d been working on hearing aids. Like, duh, wasn’t that already obvious by how often he was bringing her new ones?
But mostly this was good and the tension was effective, very effective for the first 2/3.