Underwater optical wireless communication (UOWC) due to the scientific, industry and military applications is important. In comparison to RF and acoustic methods, UOWC can provide a higher transmission bandwidth, higher immunity and higher data rates. However, UOWC systems suffer from severe absorption, scattering and turbulence introduced by underwater channels. In this thesis the complete model of UOWC is investigated and the simulation results is compared with the published experimental results to verify the validity of the simulations. The proposed model consists of the transmitter, under water channel and the receiver. In the channel, all the important factors which affects the light including scattering, turbulence and background noise are considered. Scattering noise for the first time is investigated and considered in our model. Comparing the simulation results with the published experimental results validate our model. The relationship between bit error rate with the dissolved particles in water, turbulence, link distance and laser beam divergence have been investigated. Key words: UOWC, scattering, turbulence, scattering noise.