Li Hui's words have a deeper meaning. Where is the real prince of water?

I think the real hiding place of Shui Jun should be a place that I never want to talk about. Every time he mentions that place, he always shows great despair. The characters in that space are absolutely unusual. Moreover, according to the French king and Yan Jue, the space where the prince of water is located should be called doomsday, and there are probably rulers there.