In this study, the Brazil nut segregation problem was experimentally investigated in a 3D vertically vibrating granular bed. A high-speed camera was used to record the rise time of larger particles (i.e., intruders). The results showed that the rise time decreased with an increase in the size ratio of monosized immersed granular materials. The percolation effect is the dominant mechanism that influences the Brazil nut segregation behavior of monosized immersed granular materials. The percolation effect is stronger when the size ratio is higher, leading to a stronger Brazil nut effect. In addition, the results indicated that the rise times of the intruder are shorter with multisized immersed granular materials than those with monosized immersed granular materials. The rise velocity does not increase monotonically with an increase in the filling bed height. In addition, the base roughness significantly influences granular segregation. The Brazil nut effect is mitigated, resulting in longer rise times with the bumpy base. (C) 2015 Elsevier B.V. All rights reserved.