It looks like hes talking about drowning someone (face down beneath the waterline/gazing into the deep); the "piercing sounds" would be the victim's screams. Once the person is killed, all thats left of him/her are the scars he/she left on the narrator.
Salvation for the victim comes being murdered, and in commiting the murder, the narrator has lost his deliverance.
It looks like hes talking about drowning someone (face down beneath the waterline/gazing into the deep); the "piercing sounds" would be the victim's screams. Once the person is killed, all thats left of him/her are the scars he/she left on the narrator.
Salvation for the victim comes being murdered, and in commiting the murder, the narrator has lost his deliverance.