Harry's gone aquatic; with his head underwater, the only sounds in the room are Draco’s fast breathing and the gentle slap of waves against the sides of the little pool they’ve conjured.
The water is warm, though not as hot as the wet inside of Harry's mouth.
Draco spreads his legs, but he can't get any closer to Harry. Harry's taken Draco's whole cock neatly down into his throat, bobbing and sucking in perfect merciless rhythm.
Draco clutches at Harry's shoulders, desperate, on the edge, and as he lets go, his fingertips drift over the undulating edges of Harry's temporary gills. That shouldn't be sexy, fuck, that shouldn't be —
Draco groans, coming. Harry's webbed hands stroke up his chest in encouragement as his spend is swallowed neatly down.
"Fine," says Draco, when he can catch his breath. "Fine, you're right. It's different when you don't need to breathe air."
Harry can't talk, but the Gryffindor arch of one brow says it: I told you so.
165 words for the @drarrymicrofic prompt "inhale", with thanks to @dodgerkedavra for the quick helpful beta