I personally enjoyed this movie. Contrary to multiple reviews calling this dry or a fantasy wannabe (something along those lines), I think the story is effective in portraying its purpose. There is a good deal of artistic animations parallel to the protagonist's interests—drawing, making graphic novels—which is a great detail to add to this movie.
[⚠️ Some spoilers for those who have not watched]
However, I do think that there's some unresolved points in the narrative, especially around the Water Man and Jim Bussey.
The movie makes it's audience believe that the Water Man is a real entity, which is supported by the character Jim Bussey who forwards the movie by giving protagonist Gunner Boone a means of meeting the Water Man. Gunner then realizes that it was his imagination that drove the adventure, and it was his hope that reinforced the "signs" he experienced on the way to the Water Man's place. The entity he sees turns out to be only in his imagination. Jim Bussey's belief in the Water Man's existence is never resolved by the end of the movie.
The expectations for the fantasy hype of this movie is let down successfully, in my opinion, but it wasn't done neatly. There are still some loose threads like I mentioned. The message of hope, death, and cherishing time with your loved ones was well delivered. If given more time for revisions, the movie would've been better. Despite that, I still enjoyed the movie. 3 stars for successfully entertaining me and my family.