reflects water spear

A normal person would have been too surprised to react and simply been skewered.
However, Accelerator was not bothered by it. He himself was a mass of the mysterious.
He held up his right hand, the sole area his reflection was activated on.
The water spear was smashed to pieces.
The water turned to a rainbow of light that flowed diagonally back from his right hand.
It acted as a wall of pressure that knocked away four of five of Vodyanoy’s comrades.
Accelerator had blocked the attack, but he frowned.
He couldn’t figure it out.
If his reflection had succeeded, the water spear should have head straight back at
Vodyanoy and pierced her arm. Instead, it had gone astray and had disintegrated into a
rainbow of light. It had been an odd phenomenon. It hadn’t been something like steam
created from water or ice. Accelerator had caused the reflection but he didn’t
understand the process by which it had turned to light.

- Toaru Majutsu no Index Volume 20, Chapter 2 Part 10