By assuming the fluid is incompressible and
at rest, the hydrostatic pressure distribution is expressed as:

p_{1} = ρgh
+ p_{0}

From standard handbooks, it is noted that the atmospheric pressure at the sea level is p_{0 }= 101.3 kPa and the acceleration of gravity
is g = 9.8 m/s^{2}. At fresh water temperature of 16^{o}C,
the density of water = 999 kg/m^{3} and the density of seawater = 1030 kg/m^{3}.

Problem Diagram II

The absolute pressure at a depth of 12 meters of water is
p_{1} = (999 kg/m^{3}) (9.8
m/s^{2}) (12 m) + 101.3 kPa
= 219 kPa

whereas for seawater:
p_{1} = (1030 kg/m^{3}) (9.8
m/s^{2}) (12 m) + 101.3 kPa
= 222 kPa

Therefore, it can be concluded that the density of the fluid (fresh
water vs. seawater) in this scenario plays a very small role (1%) in
the design criteria.

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