When Hwang Tae-kyung stands at the edge of the swimming pool and looks down at Go Mi-nyu in the water, his hair changes from wet to dry. When he's filmed from a camera perspective beneath the water, his hair is wet and hanging in front of his face. Once the camera changes back to pool side, his hair is dry and out of his face.
By this time, both Go Mi-nyu's and Hwang Tae-kyeong's facial injuries (cut and scabbed lips) have completely disappeared.