in the middle of the ocean

I was writing my novel and I put in a metaphor involving the ocean. (Specifically, it was going off the "no man is an island" saying and suggesting that maybe people are islands, albeit islands that drift through the oceans and occasionally bump into each other, like people interacting with one another.)

I delved into that metaphor and had the narrator imagine if it were literal because that's the kind of thing he'd do and I figured it'd be a good metaphor to explore. And then I was suddenly struck with the realization that it would be absolutely terrifying to be in the middle of the open sea. Like that's what I thought of, being underwater in the middle of the ocean. I mean imagine you were underwater and could still breathe or something but you were in the literal middle of the ocean, like you couldn't see the surface or the bottom and you were just in the middle of that vast expanse of water that covers most of the globe.

This is the stuff that gave me nightmares as a kid and gives me nightmares sometimes now.