In this paper, the effect of ocean-land mixed propagation path on the lightning performance of grounding rods is investigated. This effect is focused on two problems. The first is extracting exact equivalent circuit of grounding rods in the presence of oceans. The equivalent circuit can be used in transient analysis of power systems in the neighboring oceans. In the second one, this effect on the grounding potential rise (GPR) is investigated. Using the obtained GPRs, the effective length of vertical rods under such an effect can be easily investigated. The simulation results show that for grounding rods far from the ocean, i.e. greater than 15 m, such an effect can be disregarded.