u/BoOgAbOoSaD

From what I remember about this book, I read it between 2016-2018.

The premise that I remember is basically this family moves to like a lake island or something, The house is nice but it's old. And it's a mom a dad a brother and a sister.

And then I think the brother has it's either his friend or like a best friend that is also there a lot. But the little sister finds this book in a hidden room and it's like a journal and she's reading about it but she can't understand it because none of it seems to make sense to her.

And they find like this hidden bunker The kids do, but before they can really explore like this group attacks them and I can't remember if it's soldiers (enemy), cultists, or something but I know that the friend was involved with the attackers. And the whole family ends up somehow involved and fighting.

At some point like a fog or something rolls in and this ghost submarine from a past war (I'm thinking ww2-vietnam era) shows up and the ghost soldiers basically kind of attack like anything sort of but I think that they avoid harming the sister. But they end up and like this time loop and in the bunker the door is locked and water's flooding it so the ghost soldiers are going back through the motions of drowning again but they're also taking I think the brother, the father, and the friend with them but somehow the door gets broken like they get out.

The ending of the book was weird and very hazy to remember but I think it ends in the dad and I think either the friend or the brother getting taken by the ghost into the submarine and then disappearing back into the water. And the book ends with the sister's point of view of them having to move on with the fact that they can't even really go to the police about this because obviously ghosts.