A jet velocity measuring apparatus is disclosed for measuring the velocity of a fluid stream. The apparatus (10) measures the time delay between primary electronic signals generated by a first photosensitive device (32) as a result of a first beam of light from a light source (34) being reflected by a portion of the surface (S) of the stream (24) and secondary electronic signals generated by a second photosensitive device (36) as a result of a second beam of light from a light source (38) being reflected downstream by substantially the same portion of the surface of the stream (24). The apparatus includes a housing (22) disposed parallel to the plane (P2) of the surface of the stream. A first and a second fiberoptic bundle (42, 44) transmit light from the light source (34, 38) to the surface of the stream (24) and back respectively to the photosensitive devices (32, 36). Debris-deflecting slots (88, 90) are disposed adjacent to the housing (22) for deflecting debris therefrom.