The present paper deals with the investigation of plate type fuel assemblies immersed in still water under simulated seismic load. In a typical high flux reactor, plate type fuel assemblies are closely arranged to achieve the high neutron flux. The coolant filled gaps between the fuel assemblies play a significant role in determining and altering its dynamic characteristics. To account the added mass and damping effects posed by the fluid film present in these gaps, a number of experimental and numerical case studies are conducted for a specific range of fluid film thickness for single and double plate systems (SPS and DPS) and square channels. A coupling beat phenomenon has been observed in DPS for a certain range of fluid film thickness. To investigate the beating phenomenon further, wavelet analysis is performed to identify the frequencies in the vibration of submerged plates. It is observed that added mass coefficient (cm) follows a linear relation while the damping coefficient (cv) follows a cubic relation with fluid film thickness. It is also found that maximum displacement of the fuel assembly is significantly small than the fluid film gap, as per the present correlations under the seismic load.