He was floating.
It was dark, very dark, and then suddenly: stars. They shimmered at the edge of his vision, not acting like proper stars at all. They moved when he tried to look at them, and changed color, and twinkled all wrong.
There were stars, and he couldn't breathe.
Breathing out, now, breathing out was easy. Sort of easy. The air in his lungs felt stale and heavy - apparently he'd been holding his breath for some reason. Ah well, out with the old and in with the new. He pushed the air out, feeling his stomach muscles firm. Air swished through his nose, making a sort of a sighing noise. He didn't usually notice the noise, but today it seemed oddly relevant. Generally after that the air tended to rush right back in, but not this time. This time there was nothing. His throat convulsed a bit, trying to pull the air in, but there was some sort of shortage going about.
The stars were multiplying, either that or getting bigger. His whole field of vision was filled with them now. They shimmered and danced. They were singing, even, a high sweet song that tickled at the roots of his hair. He wanted to laugh, but it was odd how he'd never noticed before that laughing required breathing. He got out a single "ha" and then half-choked trying for another. His throat was really spasming quite a lot now, but his mind was floating away in a warm, sweet haze. He was suddenly incredibly sleepy. Maybe he'd take a little nap. The stars were really quite comforting in a way, despite the slight tinniness of their lullaby.
He closed his eyes but the stars were still there.
Then the stars exploded into sparkles and lips covered his, a sloppy kiss. The lips were warm, beyond warm. They nearly scalded him. A tongue shoved urgently against his. Warm spicy air flooded his mouth, puffing out his cheeks, and he gulped it into his lungs. The stars began to recede, their song reduced to a faint hum. His eyes sprang open. He was still floating, still dizzy, but his mind was coming back. Something had gone very, very wrong, nearly all the way wrong. The person kissing him pulled back and stuffed a mouthpiece back into her mouth. Her chest heaved as she sucked at it.
"River?" he said with a bit of the air she'd given him.
"Breathe out," she commanded around the mouthpiece. He envied all the air in her lungs. He fought it for a moment, but then exhaled. She kissed him again, breathing into his mouth. The air rushed out of her and into him, flooding him with heat and relief and the perfume of her. He felt as if the molecules of her air were rushing all through him, into every part of his body, reviving each and every desperate cell. There was no part of him River's air couldn't find, no part of him her air didn't touch and caress and coax out of starry vertigo. Her air claimed him. It was incredibly, indelibly intimate. He felt his body stirring. Her lips were intoxicating; her tongue brushed his and he shivered. She wrapped one arm tight around him and he clung to her. They breathed together for a long moment before she pulled back again. The Doctor held onto his last bit of air and looked around. The TARDIS hung below them, door open and inviting.
"What happened?" he asked, releasing the air.
"I just got here," she said, and sucked another breath from her mouthpiece, letting the air flow into his mouth. Every breath from her pushed the stars a little further away; he could barely hear their song now. He held the air as long as he could, though he could feel the dizziness creeping back after a moment. The tingle in his limbs was caused half by her presence and half by the distress of his body; it was an interesting sensation. He held out a little longer, swooning back into the starry glory, and River made an angry noise and kissed him hard. She breathed forcefully into his mouth, her fingers pinching his nose shut, and he took in the damp heat of her air. His lungs filled until his ribs nearly creaked. River was so warm against him, and everything else was so cold now.
"Oh, stupid, stupid Doctor." She took a breath from her air supply and shoved the mouthpiece into his mouth. He gasped, filling his lungs. "How did you forget the air corridor?"
"Not sure," he said, passing the mouthpiece back. "Not sure how I ended up here at all." That was all of his air. His lungs cried out for more as he held out against the need to breathe. It seemed rational to ration the air supply - he wasn't sure how much River had in her tank and he wasn't entirely certain how to get back to the TARDIS. Besides, it was delicious to fall almost all the way back into his fever-dream of stars, and to have River bring him back from the very brink. The light glittered in the halo of her curls. Her body pressed against his as if they weren't drifting in space, as if they had no concerns beyond the needs of their bodies. Well. He supposed they didn't, but it wasn't quite the same. She made an impatient noise and gave him three deep breaths, nearly shoving her air into him. He did his best to take in every bit of it, feeling his mind return.
"If you want to suffocate, there are better ways," she said, and gave him the mouthpiece again. He sucked at it, missing her lips. She flung both arms around his neck, hooking one leg through his. He couldn't help thrusting lightly against her, setting them spinning, which made him dizzy all over again. River tutted and tapped coordinates into the vortex manipulator on her wrist and with a zap, they were back in the TARDIS. They tumbled to the deck, the Doctor making sure that River ended up on top. The impact of it nearly knocked the air from his lungs, but he held onto it, gasping only a little, though the mouthpiece of the air tank fell away.
"Idiot," she said. "Isn't there some kind of automatic setting for the air corridor, in case of things like this?"
"Not sure," he said. "Perhaps there ought to be."
"You're lucky I picked up on her distress call," she said, shifting half-off of him.
"You won't always be around to save me every time I jump out of a spaceship?" he suggested.
River gazed at him and leaned down for a very lingering kiss. He pushed up against her mouth, his body rising under hers. It was an interesting response to nearly dying, the sudden hunger that rushed through his body. He decided not to question it.
"Well, hello, sweetie," she said, raising an eyebrow at him. "If you want to try asphyxiation, I suggest that you do it somewhere with a safe word next time."
"I told you," he muttered. "I don't know what happened."
"I'd be perfectly happy to oblige you," she said. "You don't have to go to such ridiculous lengths. There's a whole bondage planet, after all." She smirked. "Just look at you blush."
"We can stick to the regular way for now," he said shortly.
"Right now?" she asked, her hand wandering down his body. The vortex manipulator on her wrist scraped enticingly along the seam of his shirt and nearly caught on the waist of his trousers. He was already ready, straining a little against his trousers, and River smirked at him again.
"Yes, please," he said, unwilling to question it too much, but she laughed and kissed him again, their breath mingling warm in the space of their joined mouths.