In this study, oil spill development in the Marmara Sea is numerically studied by a stochastic approach. The model is based on a flow field computed by finite element discretization of the shallow water equations. A stochastic Lagrangian particles cluster tracking approach is adopted for the simulation of the oil slick movement. It is shown that the timescale of a major spill is as short as a few hours. The Turkish straits system is made up of the two narrow straits of Istanbul and Dardanelles that are connected by an inner sea, the Sea of Marmara. Caspian, Central Asian, and Russian oil and gas resources are transported through this major energy hub to the Mediterranean and the rest of the world. The enormously increasing maritime traffic density alarms the development of environmental management tools for pollution prevention, prediction, and risk assessment. This model we present for the Sea of Marmara extends our previous models for the Istanbul and Dardanelles straits, and completes a mathematical prediction tool for this fragile environment.