Intriguing and Philosophical:
* The Water Within: A Journey to Understanding Ourselves
* More Than H2O: The Essential Essence of Water in Our Being
* Liquid Life: Exploring the Unseen Connection Between Water and Us
* The Symphony of Water: A Composition of Our Very Existence
* From Ocean to Cell: The Unbreakable Bond of Water and Life
More Direct and Engaging:
* Why You Are Mostly Water (And Why It Matters)
* The Secret Life of Water: How It Shapes You and Makes You, Well, You
* Water: The Blueprint of Life
* The Amazing Truth About What Makes You Human
* The Water We Are: A Celebration of Our Liquid Connection
Short and Catchy:
* You Are Water
* The Power of H2O
* Water: The Essence of Life
* Liquid You
Ultimately, the best title will depend on the tone and style of your passage. Consider your intended audience and what kind of impact you want the title to have.