Final answer:
The water pressure surface, or potentiometric surface, refers to the level at which water pressure is equal throughout a fluid. When submerged in water, the pressure is the same at all surfaces of an object. The increase in pressure when submerging a hand in water is called bulk stress.
Step-by-step explanation:
The water pressure surface, also known as the potentiometric surface, refers to the level at which water pressure is equal throughout a fluid. When submerged in water, the pressure is the same at the top, bottom, sides, and surfaces of an object. The increase in pressure when submerging a hand in water is known as the bulk stress or the difference in pressure compared to the normal level.