That's the sound of snapping shrimp - music to oyster ears. Dr Dominic McAfee has been playing this sound underwater to help regenerate natural oyster reefs. He's been doing this work for years, but recently, there's been an upswell in interest, as the South Australian government tries to increase resilience against a harmful algal bloom. The ongoing environmental crisis has killed hundreds of species and resulted in tens, possibly hundreds, of thousands of marine deaths. Dr McAfee says South Australia used to be home to huge oyster reefs, which would have curbed the intensity of the algal bloom because they naturally filter the water. He’s speaking here with SBS's Tee Mitchell, who started by asking about the role and extent of oyster reefs before colonisation.