what is pip's experience when he is adrift out in the ocean?

Pip experienced the worst kind of loneliness.

"Now, in calm weather, to swim in the open ocean is as easy to the practised swimmer as to ride in a spring-carriage ashore. But the awful lonesomeness is intolerable. The intense concentration of self in the middle of such a heartless immensity, my God! who can tell it? Mark, how when sailors in a dead calm bathe in the open sea- mark how closely they hug their ship and only coast along her sides."