Is this motion blur?

I’ve got a problem with my map that I assume is motion blur, I’ve attached a ppv and set the amount to 0 and its made no difference.

It only happens on the blue water material and is clearly the white wall material.

There’s no overlap there at all, the white wall and platform is well clear of/above the water material and its only apparent when the player character is in motion.

Any ideas?

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