The Bulk modulus for an incompressible liquid is

Since liquid is incompressible there is no change in volume. When strain is small the ratio of the normal stress to the volume strain is called the bulk modulus of material of the body. $\mathrm{B}=\frac{\text{ normalstress }}{\text{ volumestrain }}$ =normal stress change in volume/ original volume since, the liquid is incompressible change in $\mathrm{B}=\frac{\text{ normalstress }}{\mathrm{o}}=\infty$