Pressure acts in every direction
The pressure that arises in a liquid acts not in one direction but in every direction. A simple experiment shows it.
The experiment
Make holes here and there all around a polythene bag. Fill it with water and hold it up by its mouth.
Figure to be added
The observation
Water comes out of every hole — not just the ones near the bottom, but the ones on the sides and the ones facing upwards as well.
What this tells us
Each hole is on a different side of the bag. Water still leaves through every one of them, and it does so because there is a water pressure at the place where each hole sits. If the pressure acted in one direction only, water would leave through the holes facing that way alone.
The first property
At a given point inside a liquid, the pressure takes the same value in every direction.