Presented by Welsh acting legend Dame Sian Phillips, this final episode in the series looks at some of the biggest challenges and issues facing the marine environment in Wales and the rest of the world today. We meet the conservation heroes from across Wales, each doing their bit in many ways, to help marine conservation and promote the importance of the ocean: from fishermen sacrificing profits in return for sustainability and a plastic-waste campaigner who paddleboarded around Wales to raise awareness about the pollution of our oceans to a group of underwater scuba-diving litter-pickers and a surfer who uses the sea to help people with mental health issues.

Many are also working directly to save marine wildlife, including a highly successful breeding programme to bring seahorses back to Welsh waters and remarkable organisations rescuing Atlantic grey seals and stranded whales. When the tide goes out, one group of young enthusiasts undertakes important species counts on Welsh shores, and another young marine biologist heads out to sea using a bait camera to film shark and other exciting species, which he records and then shares with the world via social media.

We also join the remarkable world-leading Welsh Seagrass Project, led by a passionate scientist who is trying to plant a million seeds in Dale in Pembrokeshire. Seagrass is a hugely important marine environment. It acts as a nursery environment for animals and stores huge amounts of carbon dioxide - but seagrass has been disappearing across the world due to human activity. Show less