Charles Ellicott Commentary Acts 8:38

"And he commanded the chariot to stand still: and they both went down into the water, both Philip and the eunuch, and he baptized him." — Acts 8:38 (ASV)

They went down both into the water.—The Greek preposition might mean simply to the water, but the universality of immersion in the practice of the early Church supports the English version. The eunuch would lay aside his garments, descend chest-deep into the water, and be plunged under it in the name of the Lord Jesus; the only formula recognised in the Acts. (See Note on Acts 2:38.) So it was, in the half-playful language in which many of the Fathers delighted, that the Ethiopian changed his skin (Jeremiah 13:23).