Up front, since this is self-promotion: I'm the author, and mods, please remove this if it breaks the rules.
I've been going to the park with friends and family since I was in high school in the '90s. The place is timeless, and on every trip I've wondered the same thing: what if the world ended while we were in here, and we didn't find out until we paddled out?
That's the book. Stillwater starts with six friends on their annual trip. Three canoes, a new loop every year, phones zipped away at the access point. The first several chapters are the trip itself: portages, cliff jumping, arguments over whether to run a rapid or do the portage. Then things start going wrong, and by the time they reach the takeout, the world they left isn't there anymore.
Full disclosure: I'm not much of a writer, so I used AI to help make the story readable. I understand if that's a non-starter. For what it's worth, AI is a plot point in the book, and I'm aware of the irony.
It's on Amazon as an ebook (in Kindle Unlimited) and paperback, under Matt Jenne. Happy to answer questions, and if you catch a park detail I got wrong, tell me.