Over the pat decade of more we have been sumilating the transport of buoyant debris across the Indian Ocean through coupling hydrodynamic with particle tracking models. The simulation include simulating: (1) the debris originating from the MH370 aircraft and team accurately predicted the landfall of the debris in the western Indian Ocean more than 12 months prior to debris coming ashore; (2) transport and beaching chracteristics of plastics introduced fron riverine sources in the Indian Ocean; and, (3) transport of 78 tonnes of nurdles spilled into the ocean through a ship accident off the west coast of Sri Lanka. Challengers and lessons learn from each of these examples will be presented and highlighted. In particular, the requirement for different and time scales will be discussed. These examples include multi-year simulations that include seasonal and inter-annual variability.