Moriarty scares John more than anything.
He's never seen Sherlock like this. The consulting detective has been puzzled, irritated, infuriatingly arrogant and, on rare occasions, challenged.
This is different.
James Moriarty is different.
He's quick and he's dangerous and he's clever. He is oh so clever... He's as clever as Sherlock, John thinks. And if not as clever, then close enough that to John it doesn't matter. The Troposphere and the Thermosphere might be miles and miles away from each other, but there far enough away from John that the distance looks small by comparison. It doesn't matter to John who's cleverer, not really. The only thing that really matters is what Moriarty does to Sherlock. And Moriarty does do something... Even if John doesn't know quite what it is, he's knows that it's there. And he hates it.
It comes to a crux at the swimming pool. It's terrifying, the echoes, the taunts, the goddamn bomb... John thinks that they'll die this time. Doesn't see how they won't, not this time. His death doesn't bother him too much. Sherlock's does. He'd like to trust the detective to get them out... but he doesn't think he can. Not this time.
Because Moriarty is good. So goddamn good...
They leave because Jim Moriarty lets them, not because of Sherlock, not this time. They live because Jimmy decided he wanted to play another day...
It scares the hell out of John. More than he's ever let Sherlock know - he never will let him know.
If there's one thing John Watson can hide from Sherlock Holmes, it's his feelings.
