Watching Iron Lung a second time and really looking out for it, I love that the SM-13 seems to be alive almost immediately and seems to care about Simon. At least, it cares about him as much as Simon cares about himself. I think it becomes a part of him, and him a part of it, basically as soon as he's dropped in.
Things in the Blood Ocean become part of the Blood Ocean. The SM-13 has gone down more times than just with Simon in it. It has all of those who died in it within it, still, same as the SM-8, including the Eden member whose last wish was to leave some hope and guidance for the next of his brothers to face the same fate. That care, that love, and the care and affection that Simon treats the ship with, that congeals into something alive. An expression of that care and that hope, the same way the SM-8 became an expression of fear and regret.
It makes shadows and shapes to lead Simon to the computer. It sparks and flashes to help him find the crawlspace, then makes more shadows and noises to guide him to the engine restart and the push to close button.
As it becomes more organic, it holds down the camera button by growing an X of flesh over it, just like Simon tried to do with the tape, letting him see so he can escape the SM-8.
Even when it's growing over him, it's not malicious. It just is. And it is as it's perceived to be. As all things in the Blood Ocean are. Which, again and again, is something Simon trusts and cares about. Something that protects and provides for him. That sweats and bleeds as he sweats and bleeds. That both frees and imprisons him. That breathes for him.