It's the fact that he falls that keeps Jacob from killing him, that instead Jacob slices open his radiation suit at the shoulder and bites into the flesh underneath, opening a deep cut that bleeds heavily. He hits his head hard against the wall and goes down.

He stays conscious, barely. He can taste blood in his mouth. Bit his tongue, probably.

Doesn't matter. He's in the water.

And so is Leonard.

Chronos might be heavy, but he's fast. He turns on Leonard, keeping on arm up between him and Jacob to take any further attacks, and lunges, seizing Leonard by the throat and pushing him down until he's submerged.