This paper investigates the effects of mesh resolution on the numerical modelling in coastal studies. Flexible meshes with different resolutions are generated by DHI software packages and then applied to simulate flood events. The performance of the meshes is summarised and compared, which shows the model with higher-resolution meshes produces more accurate hydrodynamic results. The performance of the mesh structure in the simulation depends on the flow magnitude, and therefore, a higher-resolution mesh is required when a higher-magnitude flood event is investigated. A case study of a high-resolution unstructured mesh was proposed for Moreton Bay in Australia, which was expected to lead to useful suggestions for further studies for this area.