The quasi-bound biological or structuredwater molecules in a protein play a key role in many biological processes. The dynamics of the biological water has been studied by femtosecond spectroscopy and large-scale computer simulations. Solvation dynamics of biological water displays an almost bulk-water like ultrafast component (∼1 ps) and a surprising slow component at the 100–1000 ps time scale. In this article, we discuss several examples of the ultraslow component, its possible origin and implications in biology. We show that the ultrafast (∼1 ps) component arises from an extended hydrogen bond network while the ultraslow component originates from binding of a water molecule to a biological macromolecule.