"I don't know about your kind," he says, "but for humans - there's an instinct to this. A fluidity." He lets her grasp him tight; his own is firm, but not desperate. "You can let the water carry you."

He lets the water lift her, slowly decreasing the amount of force he uses on her back. Tries to think back to when he learned to swim, but it's too far buried in the vagueness of memory. He just knows how to move now. The memory, the knowledge, is physical.

"Sorry," he says. "It's hard to describe something that feels natural." Without resorting to pure terms of physics.