The effect of nozzle geometry on maximum bubble penetration depth in a vertical liquid jet aeration system is investigated in relation to jet surface disturbance and air entrainment rate. The penetration depth decreases with increasing dimensionless nozzle length up to 15, but is constant with the dimensionless nozzle length above 15 for nozzles of contraction angle below 90 degrees. The penetration depth is independent of the nozzle length for nozzles of contraction angle 90 degrees. The effects of other parameters such as jet length and jet velocity on the bubble penetration depth were also evaluated, and an empirical correlation is presented for predicting the maximum depth of bubble penetration induced by a vertical liquid jet as a function of the operational conditions and nozzle geometry.