speed of light in water ##v=225,407,863.2″ “##meter/second
Formula for refractive index
##n=c/v## where ##” ” “n=” “##refractive index
##” “c=299792458” “##speed of light in a vacuum in
##” ” ##meter per second
##” “v=##phase velocity of light in the medium
Solve for ##v##
##v=c/n##
##v=299792458/1.33##
##v=225,407,863.2″ “##m/sec
God bless….I hope the explanation is useful.