This study seeks to characterize a novel gas-liquid mixer. In this air-water two-phase flow system, liquid is pumped through a perforated plate, generating high-speed liquid jets which flow downward. The gas, on the other hand, is sparged into the flow near the bottom of the column. Large bubbles flow upward, where they are broken by the high-speed liquid jets flowing through the perforated plate, and then flow back downward as much smaller bubbles, exiting the column together with the liquid through the bottom outlet. This two-phase flow system combines several features only sparingly reported on in the literature: large column diameter (0.29 m), downflow of liquid, and a large population of microbubbles (< 0.5 mm diameter with void fraction > 0.3 in many cases). This study investigates the overall void fraction in this unusual flow system, as well as the axial void fraction distribution. The void fraction is found to fit a modified drift-flux model.