Vertical profiles of turbulent dissipation rate, current velocity, density and suspended particulate matter (SPM) concentrations have been made at three contrasting sites in the Irish Sea using a combination of moored and profiling instrumentation. Measurements were made over two tidal cycles at two well mixed and one thermally stratified site. The observations indicate that at all sites there is a strong correlation between SPM concentrations and levels of turbulent dissipation rate, both of which are closely related to the tidal flow. The principal variations in SPM concentration are due to resuspension and settling of bed material and advection of horizontal concentration gradients. Turbulent dissipation rate depends closely on local vertical shear in the horizontal velocity. The vast majority of energy is dissipated in the high shear region near the bed with higher dissipation rates measured at the more energetic sites. An M4 harmonic analysis reveals the nature of the sediment resuspension/settling and turbulent dissipation rate signals. Where confidence in the analysis is significant, the phase of both signals increases with height. In mixed waters, the dissipation rate M4 phase increases steadily up to the surface whereas the SPM phase increases more rapidly in the near bed region. In the interior of the water column, both phases increase at approximately the same rate. Density stratification has a strong effect on the vertical distribution of fine suspended sediments and the dissipation of turbulent kinetic energy. The M4 variation in both SPM and dissipation rate is confined below 40m and the phase of both M4 signals increases rapidly with height so that lags relative to the bed variation are significantly larger at this site. Semi-diurnal variation in the height of the pycnocline is a further control on the distribution of sediment in the near bed region. A 1-d, level 2.0 turbulence closure model has been used to hindcast the observations. The model is successful in simulating the mean flow, density and turbulent dissipation rate at both mixed sites. SPM concentration predictions are broadly in line with observations although simulation of the phase relationship between dissipation rate and SPM is only partially successful, probably because the model over-simplifies the nature of the sediment population. At the stratified site, limitations in the model's ability to accurately simulate the density field mean that the SPM results deviate from the observations.