The same at the same level
At the same level in a liquid, the pressure is the same everywhere. Showing it takes nothing but a plastic bottle and some water.
The experiment
Pierce several holes low down on a plastic bottle about 25 cm tall, all at the same level. Now fill it with water.
Figure to be added
The observation
The water leaving all of the holes travels the same horizontal distance.
How the distance reports the pressure
The speed at which water leaves a hole depends on the pressure at that hole. A greater pressure sends the water out faster, and faster water travels further horizontally before it lands. Since the water from every hole went the same distance, the pressure at all of those holes must be equal.
The second property
At all points lying at the same level in a liquid, the pressures are equal.