Kapitel 1932: "Independent Space" 

At the same time, while Ainsley was trying to use her 3D map ability, a certain invisible ghost, the Godfather, who had been clinging to Ainsley like an aggrieved pet, finally showed his presence to Ainsley. 

[Little lass, I think this is still in the lake and not the deep sea.] 

[Although it feels similar to the environment in the deep sea, it's impossible for the assessment staff to let you guys be teleported away from the island so easily.] 

The only explanation was that, this place was still in the lake, but it might be an independent space which was why even though the depth of the lake should not be too deep, there could still be a place like the deep sea here. 

The Acacia Town was also a strange existence that should not exist if they followed the original terrain, but it did exist anyway. 

This place should be that place beyond the 'layer' that the group could not pass through before they went to Acacia town.