Ocean currents transport many particulates throughout the ocean, from larvae to pollutants. Understanding these transport pathways, and their variability, is essential for many applications, such as marine conservation and pollution attribution. However, many types of particulates are too small to be tracked directly. This project is a numerical model-based investigation of marine dispersal in the western Indian Ocean, one of the least-studied parts of the global ocean. It specifically looked at two applications of marine dispersal: marine plastics accumulating at remote islands, and coral reef connectivity. To predict the sources of debris (both terrestrial and marine in origin) accumulating at remote western Indian Ocean islands, large-scale Lagrangian analyses were carried out incorporating beaching, sinking, and the effects of ocean currents, winds, and waves. The raw data from these Lagrangian analyses are archived here, from which source analyses can be carried out for various parameters using the associated scripts. To assess the connectivity of coral reefs across the southwestern Indian Ocean, we firstly ran a high (c. 2 km) resolution ocean simulation in a 28-year realistic, and 10-year climatological, configurations. The model output is available here in full, including high (30 minute) temporal resolution surface velocities. Daily Lagrangian larval dispersal simulations from all reefs in the southwestern Indian Ocean from 1993-2020 were also carried out. The raw output is archived here, and can be converted into larval fluxes (incorporating biological parameters such as mortality and competency) with the associated scripts. This work was funded by NERC Doctoral Training Partnership in Environmental Research grant NE/S007474/1 awarded to Noam Vogt-Vincent.