The discussion centers on the phenomenon of water receding from the shore prior to a tsunami wave peak and how this differs from regular wave behavior. The receding water, or leading wave, is characterized by a drop in water level, which can also be an elevation in sea level, depending on the wave's characteristics. This behavior is attributed to the physics of wave propagation, where a single tectonic plate upthrust generates a series of waves, similar to the ripples created by a stone dropped in water. The amplitude of tsunami waves increases as they approach shallower depths due to conservation of energy, leading to a phenomenon where the wave's velocity decreases. The discussion highlights that tsunamis can have smaller precursor waves and emphasizes the complexity of these events, including the duration of earthquakes, which typically last 30-60 seconds, contributing to the series of waves generated.
