In past marine connectivity study of the GBR it has been assumed that 28% of coral larvae undergo natal settlement. This parameterisation is largely based on a field study on Helix reef (Sammarco & Andrews, 1989). In this study we present new high-resolution particle-tracking simulations for a range of GBR reefs and islands with different reef morphologies and estimate the time-scale of local particle retention. We examine the influence of model grid resolution, 3D advection and particle release time, and express retention time-scale as a function of physical parameters such as reef area, mean water depth and tidal range, suggesting ways in which the parameterisation of natal settlement might be improved in future marine connectivity modelling.