The UNESCO World Heritage site of Shark Bay is at the interface of temperate and tropical marine ecosystems, supporting high biodiversity and many iconic marine species. The marine heatwave of 2011 was warmer (+4°C) and longer (up to 3 months) than anything previously recorded. Flooding of the Wooramel River subsequently added to the impact through light reduction (suspended sediments), resulting in bay-wide defoliation of the seagrass Amphibolis antarctica. We are continuing to monitor the recovery of seagrass meadows and the long-term trajectory for temperate seagrasses in this system.