Final answer:
An ocean wave is termed an orbital progressive wave due to the circular path water particles follow as the wave moves. Surface particles orbit in large circles, while this motion diminishes with depth until there is negligible movement.
Step-by-step explanation:
An ocean wave is described as an orbital progressive wave because, as the wave travels across the ocean surface, the water particles move in a circular path, known as an orbital motion. This motion is the result of the combined effects of the gravitational pull and the wave energy moving through the water.
The wave itself moves horizontally across the water's surface at a speed often represented as Vw or Uw, which stands for wave velocity, while the water particles move in their orbits.
The path of water particles at the surface when this wave passes is circular. They move upwards and forward as the wave crest approaches, then downwards and backwards in the wave trough. Below the surface, the diameter of these orbits decreases with depth, and at a certain point, the movement becomes negligible and water particles no longer participate in the wave motion.
These repetitive and circular motions mirror what happens to a toy boat or a sea gull bobbing on the surface; the toy or bird moves up and down but does not follow the horizontal motion of the wave.