This paper studies the relationship between the characteristics of weakly turbid water and backscattered light intensity from a collimated light beam. Water properties such as particulate concentration and the presence of organic matter are considered. We present a recent model for the propagation of infrared and ultraviolet light in turbid water and demonstrate good correlation with experimental data. The effects of beam scattering and absorption are captured in the model and validated with experimental measurements. The developed sensor is found to be capable of measuring the time-averaged concentration of both suspended solid and chemical oxygen demand. The main focus of this work is for water quality monitoring but the observations are also directly relevant to underwater optical wireless communications.