Any diver can confirm that the pressure experienced
at ten metres below the surface of a lake
is substantially larger than the pressure experienced
at five metres below the surface.
Actually, at ten metres below the surface of a lake
each square centimetre of our body experiences a pressure
equivalent to the weight of a column of
10 m water
above that square centimetre,
in addition to the one atmosphere air pressure.
It totals in to about two atmosphere of pressure.
The video shows that when the pressure on the ball increases,
the air in the interior of the ball takes a smaller volume (Boyle's law).
It becomes then easier to move the plastic surface of the ball
because there is more plastic material then what is necessary
for the interior air.
Notice that any object submerged in the fluid experiences
pressure since the molecules also impact on the object.
The pressure of air on our bodies is equivalent to the weight
of 10 m of water.
That is a pressure of about
105 Pa
or 1 atmosphere.
Let us suppose that your hand, when stretched, has an area of
150 cm2.
So, when you stretch your hand,
it does not matter how it is oriented,
then it experiences a weight of about 1500 N,
which is equivalent to 150 kg,
on the palm of your hand.
The reason that you do not notice it,
is because the pressure acts on both sides of your hand.
The resulting forces are equal and opposite.
Hence, the net effect is zero.
Actually, the latter statement is not completely correct.
When you hold your stretched hand horizontally,
then it experiences slightly more pressure on the bottom side
than on the top side of your hand.
Let us assume that your hand is 1 cm thick,
then the difference is about 0.0015 N,
corresponding to 0.15 g.
So, you experience a net upward force
of that size.
You do not notice it, because the weight of your hand
is about one thousand times larger.
However, a light hot air balloon of some ten metres high,
experiences a pressure difference which is enough for an upward force
of some 5000 N.