Inclined laminar submerged plane jets were injected from a 1 cm slot into a turbulent boundary layer developed on a sidewall of a water channel. Profiles of mean velocities and longitudinal fluctuations were measured to 64 slot widths downstream of the jet exit. Length and velocity similarity scales were obtained from mean velocity data, and local values of skin friction coefficient were determined. Two maxima in the longitudinal fluctuation profiles were established and found to follow precisely loci of vortex formations. The maxima grew exponentially in the downstream direction and peaked at a location where these transverse vortices were at their full strength before coalescence. Effects of different injection angles and velocity ratios were found. Further extension of a physical model to describe the flow is validated based on correlation of mean and fluctuating velocity data with visual information.