Isekai de Mizu no Dai Seirei Yattemasu.

Synopsis

When Nagi Saejima, a carefree high school student, wakes up from a doze, he became a lake in a different world!? Nagi, w finds out that he is the "Great Spirit of Water" whose main body is the lake, heals those who suffer from injuries and diseases with the power that dwells in himself. One day, Nagi is led by a voice calling for help and summoned by a boy. That encounter will greatly change the fate of Nagi. Alphapolis's 2nd Next Generation Fantasy Cup "Unique Character Award" winner, long-awaited comicalize!! "Since I was revered, I have to save it with the power of God's healing."