The Lonely Lighthouse

Write a story set in a world where travel is primarily conducted by submarines rather than cars. The narrative should revolve around a lighthouse keeper and his unique interactions with these underwater vessels.

Delve into how such a world would function and the different societal structures it may form. Explore the interconnection between the lighthouse keeper and the subterranean seafarers, their mutual dependence and universally shared experiences of isolation and introspection, in a realm as vast and mysterious as the ocean.