The Sava River is home to an apex underwater predator, the Huchen, or Danube Salmon. When the Huchen is thriving, the whole ecosystem is healthy. With goggles and snorkels in tow, this crew of peculiar kayak-activists-turned-river-snorkelers dives deep to better understand the condition of this freshwater world. This video is brought to you by Balkan River Defence. Shot on location on Slovenia’s longest river: The Sava.