The tidal currents of the Strait of Messina and their effect on the displacement of the water-mass interface are discussed utilizing the historical velocity data of Francesco Vercelli, taken from ~100 anchor stations during 1922 and 1923. The data show a complex, strongly tidal behavior, in which speeds of 200-300 cm/s are attained over the sill. Messina is an amphidromic point for the tides of the two main basins of the Mediterranean Sea and two distinct water masses flow through the strait at different stages of the tide; the subsurface Laventine intermediate water flowing alternating with surface Tyrrhenian water flowing south. The time evolution of the interface between the two marine water layers at the semidiurnal periodicity is computed from the observed distribution of acceleration term for the baroclinic component. This interface shows large vertical oscillations with amplitudes of ~100 m intersecting both the surface and bottom. The results are in reasonable agreement with recent satellite data and other recent field observations and numerical experiments. An estimate of the mean position of the interface is made by assuming that the potential energy required to uplift the interface, from the equilibrium depth of 150 m to the observed 30 m depth over the sill, is derived from the time-independent contribution of the nonlinear field acceleration term. The results are in reasonable agreement with observations.