This paper is concerned with an experimental investigation on plane submerged water jets discharged into quiescent water in an open channel. Flows are visualized by using hydrogen bubbles, solid particles and dye. The results show that the jets attaching to the water surface by the Coanda effect are classified into six types according to their behavior after issuing from the nozzle, and that the self-induced vibration of the jet, which is one of six flow patterns, occurs under the condition of the reduced Froude numberFr *≒0.7∼1.0. An additional analysis of the photographs reveals that the self-induced vibration of the jet is caused by attachment of the jet to the water surface and the ensuing bifurcation of the jet at an attachment point, and that the frequency of vibration is independent of the water level.