I'm not sure, and nowhere found a clear declaration, just something like that.
make underwater combat and travel a bit less disorienting for players?
The deeper you get in the ocean, the outside of the screen changes a little bit to try to give you a sense of depth, and give you a little bit less visibility and a little more haze as you drop down. So it feels like you’re actually like a scuba diver who is going down deeper and deeper into the ocean. Then as you start to swim back up, that starts to clear up so you have a better sense of which way you’re going on the Z axis.
Also, from the content perspective, the spawns and the content you experience are layered on certain levels of the ocean, just like what you would find in a real ocean. So up around the top of the ocean, it’s generally very safe. There are not a lot of creatures up there, if there is there’s usually a lot of ambiance or little things floating around on the top.
The next layer of the ocean is mostly neutral creatures, and you can choose to fight if you want to, but it’s a lot of larger fish and dolphins, and big angler fish. You’ll see those and know, alright, I’m in the mid layer of the ocean based on the spawns that I see. Now, you’ll encounter some aggressive stuff in there. There will be sharks occasionally and things like that, but we try to have a strong ecosystem of these oceans so you understand.
Then you get down to the bottom, and the bottom is where you see a lot of the aggressive stuff, and it’s where a lot of the events happen. So you always have that bottom of the ocean floor to kind of navigate off of, and to use that as a point of reference.
We try to keep a lot of the content tied towards the bottom of the ocean or around the bottom so you always have a point of reference. The areas above it are more for exploration, for getting a sense of depth, and a real sense of exploring these parts of the world.