What fundamentally causes the increase in pressure as one descends into a fluid?
Answer
The weight of the fluid resting on top
The increase in pressure with depth stems directly from the weight of the fluid column resting on top of the point of measurement. This weight is caused by gravity pulling down on the fluid's mass.

#Videos
How does liquid pressure change with depth- Kisembo Academy
Related Questions
What fundamentally causes the increase in pressure as one descends into a fluid?Which two key factors determine how fast pressure increases as you move down into a fluid?In the standard pressure equation $P = P_0 +
ho g h$, what is the term $
ho g h$ commonly referred to as?What does Absolute Pressure include?Why is the simple linear pressure equation effective for most liquids like water?Why is the simple linear pressure equation insufficient for precise pressure calculations across large vertical distances in gases?Approximately how much does pressure increase in fresh water for every $10.1$ meters of depth?If an engineer uses the concept of pressure head ($h = P / (
ho g)$), what physical quantity is being expressed in terms of depth?At the molecular level, what action creates the net downward force measured as pressure in a fluid under gravity?At the same depth, which fluid exerts a higher pressure than freshwater?