"So, tell me again why we're not drowning?" Rose asked with a skeptical look. Well, as skeptical a look as one can manage while underwater.
"Same principle as why everyone we meet speaks English. The TARDIS translates for you......I'm sure I’ve explained this before," was the Doctor’s reply, though he seemed somewhat distracted by a vaguely translucent fish that was swimming past.
"But that makes no sense," she said with a frustrated gurgle. "That's language, and this is......breathing!"
“Ahh," he bubbled with understanding. "That's a human thing, insisting there’s a difference between perception and existence. There really isn’t.”