A three-dimensional twisted hydrofoil with an attached cavitaty closely related to propellers was observed with a high-speed camera at the University of Delft Cavitation Tunnel. Reentrant flow coming from the sides of the cavity aimed at the center plane-termed side-entrant flow-collided in the closure region of the cavity, pinching off a part of the sheet resulting in a periodic shedding. The collapse of the remainder of the sheet appears to be a mixing layer at the location of the colliding reentrant flows. Collision of sideentrant jets in the closure region of a cavity is identified as a second shedding mechanism, in addition to reentrant flow impinging the sheet interface at the leading edge. Fig. 7 A close-up of Fig. 6 "marked A… shows the formation of a large spanwise vortex at 2 kHz. As the main sheet collapses, a trail of very small spanwise vortices is created, merging in several distinct larger structures.