We investigate Marine Heatwaves and Marine Coldspells along the east coast of Australia, a region dominated by the complex western boundary current, the East Australian Current (EAC). We find that episodic events in the Tasman Sea (south of 32S) are the result of complex interactions between mesoscale eddies and the EAC. We describe a mechanism analogous to atmospheric blocking, where mesoscale eddies that propagate into the region from the east are able to 'shut-off' or 'reinforce' the poleward transport of warm water by the EAC. A timescale separation between the eddies (identifed by anomalous sea surface height) and the ocean temperature is clearly identified, with the eddies being detectable more than 50 days prior to the peak of an event. We also describe the along-shelf connectivity of these extreme events - showing that large swaths of the shelf are exposed to high or low ocean temperatures more-or-less simultaneously. We discuss the implications for our results, including the potential pathway towards early detection and prediction of extreme ocean conditions in boundary current regions.