[Spoilers for Sunshine are ahead.]
He is never going to be warm again.
It's the only thought in Mace's head, other than telling himself over and over that he's a fucking idiot, that he must dive in a third time, that he has to suck it up and do this. The cold sinking into his bones is nothing. He is nothing, just another tool. He has to right the wrongs they've made because if they don't -- well, if they don't, it doesn't bear thinking on.
Mace jerks his radio on, and it takes him two tries before he can get his words out. "Capa. Capa." He barely hears the reply, just knows that Capa is there and listening and they've had their differences, but they're the last hope for humanity, and he needs Capa to understand. "We're in orbit, the computer's down. I don't know if I can get her back online. You h-have to break us out of orbit m-manually. The only way do to that is to separate the payload. D'you get it, Capa?"
He couldn't have imagined anything worse than his fifteen second jaunt in space, but Mace believes he's experiencing it. He can't feel his legs anymore. It's a wonder he's even breathing.
"Force the bomb into the sun. You have to get to the bomb an-and d-detonate it from the console." Capa says something, but Mace can barely hear him over the sound of his own excruciating breaths. "I don't know how, just do it. Just do it."
The airlock. Something about the airlock. Capa's in the airlock, and he can't do anything if he's still stuck in there, but the only way is through Icarus. Another dip into a cold he still can't wrap his mind around. He would cry, if he were the sort of man who did that. Or even if he could.
"Okay. I'm go-gonna do this."
"Copy, Mace." Capa finally sounds like he understands what Mace knew days ago. Weeks ago. They were never going to make it out of this alive, and if Icarus was going to be his tomb, so be it. She was as much a part of him as any of the other crew were.
"C-copy." He has to get back up in steps, lifting his head off the glass, putting his elbows underneath him to prop himself up. He can't feel anything, as if he isn't even in his own body anymore but merely a passenger to the cold creeping through his veins. The wrench feels almost frozen to his hand when he goes under again, and his screams are dull to his ears and his eyes burn, but he twists and he yells and he tastes the bitter, toxic coolant and reconciles himself to the idea that this is going to be his grave.
But he'll be damned if he dies before he does everything in his power to complete their mission.
With one last twist, Mace pushes himself back to the surface, clinging to the edge of the tank after he tosses the wrench aside. Every breath he takes is a struggle and he can't lift himself out, but there's the sound of Icarus's mainframe lowering behind him. Slowly, he pulls himself up, he gets his chest out of the water, his stomach, his hips--
The mainframe stops. An alarm starts sounding, and the screens go back to red. For a second, Mace can't process what's happened, but there's pressure on his leg, and the pain slowly begins to take over the cold.
"Capa!" His radio is out of reach, but he hopes he can be heard. "My leg!"
Mace whimpers and the pain shoots through him when he tries to free himself, but he's well and caught and he's going to die. He's going to die. He closes his eyes and thinks of home, thinks of the feel of what little sunshine they'd had when he was growing up, thinks of his all his friends and family he's doing this for. When he opens his eyes again, it's as if he's back in the hologram room and everything is impossibly bright. There's warmth. Some kind of warmth, and there isn't cool glass underneath him anymore, but something soft, something wet.
When he clenches his hands in a spasm of pain, it's as though his fingers are sinking into the floor, and Mace vaguely realizes he's digging into some kind of dirt before another wave of pain cuts through him and all he can do is scream.