Stereoscopic particle image velocimetry (SPIV) was used to investigate the wake of a rigid, pitching, trapezoidal panel, used as a model of thrust-producing fish caudal fins. Experiments were conducted for a range of Strouhal numbers from 0.17 to 0.56. A reverse von Kármán vortex street was observed along the mid-span of the wake whereas complexity and three-dimensional effects increased towards the tip. The phenomena of wake breakdown was investigated and shown to depend on Strouhal number. Spanwise velocity was measured in order to investigate the interaction of streamwise vortices and the vorticity created by the swept edge. Assumption of two dimensional flow at the midspan made in previous work by Green et al.1 in order to compute FTLE fields was validated by showing that spanwise velocity at the midspan is small relative to the other velocity components prior to wake breakdown. Downwash and sidewash effects were measured at quarterspan and tip location. Previously unknown upwash effects were observed to investigate the contraction of the wake in the spanwise direction. Planar laser induced fluorescence showed that large streamwise vortices create the up, down, and sidewash effects observed in the experimental results.