I'm a little late to comment but I'm catching up.

These anime that at first glance don't seem like a big deal end up being true gems. That's true, I don't remember an anime where the sea is a protagonist, it looks good, let's not lie hahaha.

I'm attracted to that mystery you mentioned, when the plots are like that that lead you down the path of despair is when I get more hooked. I don't know, let's see if I give it a chance.