I've been pondering these last few days of Simon becoming immortal somehow due to the amount of radiation he experiences and the fact that he's the protagonist in a eldritchian horror movie.
Imagine with me, a Simon who is pulled back up from the depths of the ocean, mutated and bloodied and so grateful to be alive. They grabbed the black box hours, days, weeks, some amount of time before they grabbed him from the ocean, and he's a scientific marvel, a curiosity. He's poked and prodded and he really doesn't like all that, but he sits still and stares off into space so he doesn't have to think about it. He's alive, that's what he wished for, right? He's alive, so what if he becomes an experiment?
He doesn't really, truly notice the effects until he realizes he hasn't eaten anything recently. And...he isn't hungry. Still, he asks if he can have one of the ration bars. It's...hard to get down, worse than usual. It's bland and dusty, but he eats it.
It makes him sick. An hour later he's choking it back up, watched, always watched, and shaking and vulnerable in a way he doesn't like. A few days later he tries again and it goes the same way.
So...he can't eat. He still sleeps! He can keep down water! And really, he never particularly liked the ration bars anyways. And, eventually, the COI gives him a little more freedom. Simon starts working small jobs, maybe learning under the head engineer or something.
It would be interesting if he was always the one sent back down into the blood oceans. He would fight it, and he would win until he wouldn't. Guilt is a mighty weapon. "Remember Jack? Remember Ava? You can help save humanity." And he would fold. They use his own kindness, his own guilt, against him. "You're the only one who has come back with something."
He would regret being manipulated into it every time, but it helps that he never encounters the eel again. She got destroyed by the tree he was meant to become- that he did become, he isn't sure how he survived. But he sees the remnants of the SM-14 and breaks down at one point.
It isn't until years down the line, when food becomes more scarce, when the members of COI are dying amongst themselves that he realizes that living? Isn't the blessing he thought it was, not now. The oceans have revealed nothing. He doesn't eat, he doesn't need water, he can't die (I don't think everyone aboard the stations would be thrilled about having, what could be considered, a monster aboard). Simon's sure that if he was sent on a spacewalk, he wouldn't need a suit.
Imagine with me a Simon who watches the rest of humanity die out, who is the last one drifting through space- a God looking through a pinhole, the only one left.