It's been three long years since she released "Fly," her charity single for the 2015 Special Olympics, but Avril Lavigne has finally returned with new music, delivering one of her best ballads in years in the process. And that's saying a lot: the punky Canadian pop star is at her best when she's pouring her soul out across tracks like "I'm With You" and "When You're Gone."

On "Head Above Water," released Wednesday (September 19), Lavigne pours it all out indeed—emotions flood from her like a tidal wave, drowning the listener in a cascade of hymnal melodies, heart-wrenching verses and sweeping flourishes that twinkling piano riffs and weighty strings.

A steady flow of water metaphors might sound cliché if not for Lavigne's emotionally-charged, raw vocal delivery. Each reference to the aquatic is punctuated by the singer's soulful pseudo-rasp; her heart is deep in it when she wails, "God, keep my head above water / Don't let me drown, it gets harder."

"Head Above Water" is also one of the enigmatic performer's most personal, gripping efforts to date, detailing her emotional, spiritual and mental journey during a debilitating battle with Lyme disease.

Lavigne is haunting and affecting as ever as she sings, "Yeah my life is what I'm fighting for... / ...And my voice becomes the driving force." As the production swells on the bridge, there's an air of powerful catharsis and release for the singer, who really is fighting for her life.

In a heartfelt letter to fans, Lavigne shared the devastating moment and resulting epiphany that inspired the song.

"One night, I thought I was dying, and I had accepted that I was going to die," she revealed. "My mom laid with me in bed and held me. I felt like I was drowning. Under my breath, I prayed, ‘God, please help to keep my head above the water.’ In that moment, the songwriting of this album began. It was like I tapped into something. It was a very spiritual experience. Lyrics flooded through me from that point on."

Listen to Avril Lavigne's "Head Above Water," below: