The pressure exerted by a 3000 m column of water on the bottom layer is
$P=h\rho g$
$= 3000 \,m ? 1000 \,kg \,m^{-3} ? 10\, m\, s^{-2}$
$=3\times10^{7}\,N\,m^{-2}$
Fractional compression $\frac{\Delta V}{V}$ is
$\frac{\Delta V}{V}=\frac{P}{B}=\frac{3\times10^{7}\,N\,m^{-2}}{2.2\times10^{9}\,N\,m^{-2}}=1.36\times10^{-2}=1.36\%.$