Question 1.6: The pressure at the deepest part of the ocean is approximate...

Equation (1.19)
\frac{p}{p_{a}} \approx (B+1) (\frac{\rho }{\rho_{a}} )^n -B
holds for either water or seawater. The ratio p/p_{a} is given as 1100 :
1100 \approx (3001)(\frac{\rho }{\rho_{a} } )^7 -3000
or \frac{\rho }{\rho_{a} }= (\frac{4100}{3001} )^{1/7}=1.046
Assuming an average surface seawater density \rho_{a}= 2.00 slugs/ft^3 , we compute
\rho \approx 1.046(2.00)=2.09 slugs/ft^3
Even at these immense pressures, the density increase is less than 5 percent, which justifies
the treatment of a liquid flow as essentially incompressible.