The method involves feeding gas i.e. air, to a mixing tube (2) via an air supply section (7), and feeding water via a mouth opening (13) to form a mixture of gas and water. The water is centrally introduced into the mixing tube via a feed pipe (12) and the opening, and is spread in a region of the opening by impact onto a conical body (18). The body is formed as symmetrical around an axis concentric to a center axis of the opening. A cross-section of the conical body is enlarged in a flow direction of the water. A transverse width of the body is larger than a free cross-section of the opening. An independent claim is also included for a device for aerating water, including a mixing tube.