A 1921 Western Australian tropical cyclone underscores the utility of historical records for hazard analysis in areas of marginal cyclone influence.

<p><strong>Shark Bay Marine Park is a UNESCO World Heritage Property in a region of marginal tropical cyclone influence and its sustainability requires a deep consideration of cyclone hazards. Here, we analyse historical records of a large storm surge from a Tropical Cyclone in 1921 that generated remarkable overland flow leaving fish and sharks stranded over 9 km inland. We weight information from the historical archives in a new framework and model event scenarios to reconstruct its magnitude. The plausible event scenarios imply that the cyclone was a marginal Category 4 or 5 storm with a return interval equivalent or slightly greater than the regional planning level. The outcome underscores the importance of examining the pre-instrumental events in areas of marginal cyclone influence as they are commonly of key economic importance.&#160; Our work also implies that TC risk affects marine conservation in the Shark Bay World Heritage Property and requires attention. </strong></p>