THE SLASH

The water current suddenly become chaotic and Alexander then shake his head 

He could not lose his mental right now. 

'I need to retreat first. As long as I am alive, I will have a chance to turn this back'

He turns back to see the other side of the river and he move his hand to quickly reach there.

But even before he tries to swim there, the wall of water that has appeared because of the sword strike falls back down to the riverbed and created a powerful water current.

The joined river because of the different topography on the bottom of the rive suffers some instability

Because after Aero strike, there is a large deep gash on the riverbed that resembles an abyss. 

When the river water falls back down, it fills the abyss and erode the sides of that gap which created even more erosion on the bottom of the river.