Countless marine animals frolic on the steep slopes of underwater volcanoes. In many cases, several are rare species not found elsewhere. This is in part due to the fact that plankton clings to the wall and provides the fish with food in abundance. This documentary shows several of these oases and also examines the impact dive tourism has and whether preventive measures can help to maintain them. Nature and underwater filmmaker Rolf Möltgen undertakes dives into the mysterious underwater mountain landscapes with marine scientists from all corners of the globe. This journey takes us to Mexico, to snappers, white-tip reef sharks, Galapagos sharks and giant mantas. We visit the Maldives, Colombia and Costa Rica, where the team documents rare species such as deep sea burbots, small tooth sand tiger and dogfish sharks, in depths of more than 300 metres. The eerie underwater mountain world proves: everyone plays a part in the network of life. Thanks to consistent protective regulations, it has been possible to retain the underwater diversity - especially in the unique oases of the high seas.