Proton spin–lattice relaxation of the Zeeman reservoir in the laboratory and rotating frames and of the dipolar reservoir have been studied in ferroelectric colemanite. These studies indicate the presence of two relaxation mechanisms which can be related to motions of the water molecules. The first, referred to as the flip mode and identified with 180° flips of the water molecules about their H—O—H bisectrices, is characterized by a correlation time and U-shaped relaxation minimum expected for a normal thermally activated process. The second, referred to as the jump mode and associated with a structural configuration change, produces a cusp-shaped dip in the relaxation over a very small temperature range in the vicinity of the phase transition. Above the transition temperature, the jump mode frequency is higher than the Larmor frequency and the relaxation behavior is that expected for two thermally activated processes in the white spectral region. However, in the vicinity of the phase transition, the water molecules are tightly coupled to the structure as a whole and the jump mode frequency is determined by the structural stability of the crystal. In this region its behavior is no longer that of a thermally activated process for an isolated molecular group and its frequency approaches zero critically near the phase transition.