The ocean surface is connected to water below it. Upwelling is one process that brings that connection into view: deeper water rises toward the surface as water above is displaced.
Follow the movement
In NOAA’s explanation, wind-driven movement can push surface water away, allowing water from below to replace it. Upwelled water is commonly colder and nutrient-rich, and these nutrients can support biological productivity.
Upwelling occurs in coastal and open-ocean settings. A simple diagram describes the basic process, but local conditions require more detailed information.
Draw the process in two arrows
As a reading exercise, sketch displaced surface water and the water rising beneath it. Label the arrows with movements rather than drawing an unexplained patch marked productive.
Then write what the diagram leaves out: exact depth, timing, wind conditions and local geography. Those omissions do not make it useless; they define its level of explanation.
Do not diagnose from one impression
Feeling cold water at a beach does not, by itself, establish that local upwelling caused it. A claim about a particular place needs relevant observations and oceanographic context.
Our guide to what appearances can tell you about water offers a similar distinction. A visible or felt clue can begin a question without being the complete answer.