Half of all marine life has been lost in the last 40 years. By 2050 there will be more plastic in the sea than fish. The way the ocean is different to how we thought 100 years ago. We can no longer think of it as a place of resources, a dumping ground, immune to change or decline. Blue takes us on a journey into the ocean realm, witnessing the critical moment of our time when the marine world is on the precipice. Passionate advocates for ocean preservation take us into their world where the story of the changing ocean unfolds. We meet those who are defending habitats, campaigning against exploitative commercial fishing, combating marine pollution, and fighting for the protection of keystone species. Blue comes at a time where decisions made today will pave the legacy for what we leave behind for generations to come.