This 27 January 2017 video says about itself:
Discovering underwater lake ecosystems for Blue Planet II #OurBluePlanet – BBC Earth
Brine pools are saltwater lakes at the bottom of our oceans that we know little about. Dive down into the deep sea with the Blue Planet II and Alucia Productions team to discover how they filmed the incredible ecosystems in the Gulf of Mexico.
Hear from pioneering scientists Dr Sylvia Earle and Dr Mandy Joye about why these fascinating but toxic lakes offer exciting opportunities for new science and medicine.