Population structure of many marine organisms is spatially patchy and varies within and between years, a phenomenon defined as chaotic genetic patchiness. This results from the combination of planktonic larval dispersal and environmental stochasticity. Additionally, in species with bi-partite life, post-settlement selection can magnify these genetic differences. The high fecundity (up to 500,000 eggs annually) and protracted larval duration (12-24 months) and dispersal of the southern rock lobster, Jasus edwardsii, make it a good test species for chaotic genetic patchiness and selection during early benthic life. Here we used double digest restriction-site associated DNA sequencing (ddRADseq) to investigate chaotic genetic patchiness and post-settlement selection in this species. We assessed differences in genetic structure and diversity of recently settled pueruli across four settlement years and between two sites in southeast Australia separated by approximately 1,000 km. Post-settlement selection was investigated by identifying loci under putative positive selection between recently settled pueruli and post-pueruli and quantifying differences in the magnitude and strength of the selection at each year and site. Genetic differences within and among sites through time in neutral SNP markers indicated chaotic genetic patchiness. Recently settled pueruli at the southernmost site exhibited lower genetic diversity during years of low pueruli catches, further supporting this hypothesis. Finally, analyses of outlier SNPs detected fluctuations in the magnitude and strength of the markers putatively under positive selection over space and time. One locus under putative positive selection was consistent at both locations during the same years, suggesting the existence of weak post-settlement selection.