Levi can definitely see some ghosts wandering around, but they're harmless and don't approach them. Hange is able to make some of the trees they land on sturdier by removing some of the rot they've gotten (some of the trees are worse than the others, so they should be careful traveling around, of course).

There are different types of water monsters that get to the surface to watch them. Skeletal fish with glowing red eyes, bioluminescent crayfish that shoot rocks at them and zombie (freshwater) crocodiles that occasionally jump really high to try and take a bite (easy to dodge, they're kinda slow and predictable). They're all mostly easy to deal with, but the skeletal fish just gather themselves back when they're broken apart.

However, once they get further in they will counter a boss monster. A giant squid like plant monster that is blocking most of the route forward. It has a lot of tentacles that need to be taken care of before it can be killed. It could take a long time to fight it. The tentacles use both water and mud as weapons and try to grab them to drag them into the water.

Will they fight and deal with the boss monster or will they find another way around?