General Bilgewater lore questions for rioters.

Do Pyke and Naut know eachother? Since both seem to reside in the ocean depths near Bilgewater I would assume that they have run in to each other at some point. If so what do they think of one another?

What exactly is the thing that revived Pyke? It seems whatever revived Pyke is twisting his mind in order to make him kill off a large number of Bilgewater residents and makes his list longer. Is it some shadow isles magic? or Nagakabouros reviving him?

What is the swimming city? Does it have to do with the shadow isles, which is really close or something different?