We examine the effects of sea-tides on fluctuations of the fresh-saline water interface and water table in coastal aquifers.

Time-lags of salinity were found to be much larger than that of the hydraulic head at the same spots along the interface.

In addition, the time-lag of salinity in the fresh-saline water interface was similar to the time-lag of the water table.

Tidal effect is explained by pressure wave within the saturated zone and water table attenuation due to capillary effect.

The relatively-quick pressure wave propagation causes relatively-slow fluctuations of the entire fresh-water lens.