The hydraulic response of Light Non-Aqueous Phase Liquid (LNAPL) diesel fuel to forcing by sea level changes and rainfall recharge was studied in a coastal sand aquifer. Compared to the groundwater table, semi-diurnal and diurnal ocean tides as well as longer period sea level changes more strongly affected the LNAPL appearing in monitoring wells. Changes in sea level due to passing weather systems had the most profound effect, being transmitted with 91% efficiency to LNAPL thickness in a well 135 m from the coast. The ocean boundary condition also reduced the aquifer’s response to rainfall recharge although this, and the variability of the fluid table responses, was also related to the aquifer structure. The contribution of sea level changes to varying LNAPL pressures has significant implications on the processes and monitoring of LNAPL spreading. The multi-phase processes underlying the LNAPL responses need to be clarified.