The R(v)-representation of the low-frequency Raman spectrum was used to investigate the low-frequency Raman spectrum of water. The advantages of using reduced representations in low-frequency Raman studies to display water structure are discussed. Tetrahedrically hydrogen bonded water molecules showed a characteristic low-frequency band with a peak maximum around 180 cm-1. O-18 and O-17 isotopic substitution revealed that the corresponding vibrational mode mainly involves displacements of the oxygen atoms, but no significant hydrogen motion. This mode can be used to monitor the existence of water with a bulk-like structure in biological macromolecular materials. To test its applicability NIR-FT-Raman spectroscopy was used in studies of biopolymers in order to avoid fluorescence.