This has been on my mind for a while and I just wanted some clarification.

I know we use Bismark to bring us down to the Tempests (since he was the only way of transport to the ocean's depths).

What exactly is this whole process of us being able to breathe and function down there? It looks like through Bismark we actually breach this wall in the ocean (from the top) and land on the ocean floor with water dripping on to the floor from above and puddles of it on the ground. We can all breath (which I don't think is in relation to the Kojin's magic we had to breathe underwater in SB), and there's no actual water to float around so we can naturally just walk/run on the floor.

The Sahagin as well don't seem to have any issues either though I don't know if that's because we didn't break through the wall prior and it was just filled with water.

I love the zone completely and I'm pretty sure I was just blanked out watching the story unfold to piece this together. Was it ever explained in a sidequest or is just really an obvious thing they go over?