That first evening, he finds her with her new legs dangling out the open door of the TARDIS, staring down at the Earth below and humming an upbeat tune softly to herself.

He doesn't ask her what she's thinking, merely sits down beside her and silently observes the slow turn of the planet they're orbiting. She pretends that he's been sitting there the whole time, and he pretends not to notice the way she smiles and blushes when his hand accidentally brushes hers.

The blue water that makes Earth so unique in this universe covers the majority of the planet's surface, and as she memorises the layout of where each bit of land meets the seas she allows herself to remember - and mourn, however briefly and however detached - the home beneath the ocean she's had to leave behind.

She doesn't stop her song until three minutes later, when she awkwardly shuffles closer and gingerly rests her head on his shoulder. He wraps his arm around her waist and plants a soft kiss on her forehead, and still neither say a word.

They stay like that, floating around her planet, and she thinks that perhaps she's finally found the world above she always yearned for, in this strange blue box that's bigger on the inside.