Using a highly stable spectral interferometry technique, ultrafast processes can be measured within a 2 ps temporal window. The technique was used to measure the nonlinear index of refraction due to the optical Kerr effect in water at both 815 nm and 407 nm with pump pulse lengths of ~90 femtoseconds and ~250 femtoseconds respectively. The 815 nm measurement serves as a benchmark against previous published values while the 407 nm measurement is entirely new. Knowing the value of the nonlinear index at 407 nm allows for pulse tailoring to achieve remote underwater pulse compression and self-focusing.