Mechthild of Magdeburg was a 13th century German nun who had a life-changing spiritual experience at the age of 12. Afterwards she understood that "all things are in God and God is in all things". She wrote mystical love poetry that is considered among the best ever composed.
It is thought that the author Dante based his character Matilda in The Divine Comedy on her.
This poem is called A Fish Cannot Drown in Water.
Hat tip to Poetry Chaikhana.