It was a tidal wave which I observed where the sea water rises and moves towards the coast. Tidal waves occur due to the gravitational pull of the moon and the sun on the Earth's oceans.
Tidal waves are most prominent during the occurrence of spring tides. Spring tides happen during the new moon and full moon phases when the gravitational forces of the moon and the sun align.
The interval between two consecutive tidal waves is approximately 12 hours and 26 minutes. Thus, I can expect to witness another tidal wave approximately 12 hours and 26 minutes after observing the previous one.