Bruce Dern is suspected of murder but was it Bruce or was it a swamp… thing? Spoiler, it was the swamp thing. The swamp thing, or the swamp devil, is Groot from Guardians of the Galaxy but more bloodthirsty.
The movie is mostly not about the swamp thing but the daughter of Bruce Dern (his character’s, Laura Dern is not in this movie) and a childhood acquaintance of hers as they try to prove that 90-year-old Bruce Dern doesn’t have the strength of a groot swamp thing.

It’s not an interesting story until there is a twist at around the hour mark and we get Dern acting his way out of some choppy dialogue about past grievances (aka murder). He is obviously great, and the other actors aren’t bad.
The creature, the groot swamp thing, is okay. I like the idea of monsters that are part fauna. Fauna strikes back. The CGI is fine for the budget. The few scenes with the creature and Dern would make the movie worth watching but everything in between is just so boring.
Would have worked much better as an episode of Tales from the Crypt.