Parasites aren't actually all bad – in fact, they may actually be a sign that a marine ecosystem is healthy. To learn more about the bizarre world of deep oceanic parasites, Jaida Elcock is joined by some parasitic experts. Subscribe: bit.ly/BBCEarthSub #BBCEarth #IntoTheDeep Watch more: Planet Earth bit.ly/PlanetEarthPlaylist Blue Planet bit.ly/BluePlanetPlaylist Planet Earth II bit.ly/PlanetEarthIIPlaylist Planet Dinosaur bit.ly/PlanetDinosaurPlaylist Welcome to BBC EARTH! The world is an amazing place full of stories, beauty and natural wonder. Here you'll find 50 years worth of entertaining and thought-provoking natural history content. Dramatic, rare, and exclusive, nature doesn't get more exciting than this. This is a commercial page from BBC Studios. Service information and feedback: bbcworldwide.com/vod-feedback--contact-details.aspx