What's the Name of That Book??? discussion

I mostly remember the start of the book, it follows this girl who prepares the dead to be sent out on a boat to the hole which is the afterlife, the world/people are separated into 2 different tribes that worship either the sun or moon (I think). Somehow she ends up falling into the hole, I think she follows a boy but I'm not certain. Down in the hole there is an island that is separated into the 2 tribes previously mentioned. If i'm not mistaken there is a wall that separates either side. I also remember how later on in the book we learn that the oldest are in some eternal slumber, but I may be mis remembering that part. at the end I'm pretty sure everyone on the island, maybe or maybe not including out protagonist, is sort of cycled out to make way for a new group of people to be sent to the island.

I also weirdly remember something related to coins and binoculars in this book but I don't remember where or how they fit in.

I read this around 2018-2019 and it was found in a middle school library, but I don't remember/think it's a strictly middle school level book. I remember the cover and potentially having a sunset pictured over the water with dark islands.

I also remember that it had a sequel with a dark green cover.

Since the sequel was already out by the time I finished the book, it was probably released at least a few years earlier then I previously mentioned,

When I got it from the library I remember it physically being not super old but not young either.

Edgeland by Jake Halpern?

Google Books preview:

- https://www.google.com/books/edition/...
- There are different cover images including .

Google search of Goodreads:
site:goodreads.com "fantasy" "the dead" "boat" ocean afterlife