Inside the Deadly Lakes at the Bottom of the Sea

There are lakes at the bottom of the sea. Real bodies of water, pooled on the ocean floor more than half a mile down, with shorelines, surfaces, and even waves of their own. And almost everything that swims into one dies within seconds. This is the hidden world of brine pools and cold seeps, one of the strangest places on Earth. In this documentary we descend into the so-called Jacuzzi of Despair in the Gulf of Mexico, a pool of water so salty and so toxic that its shoreline is ringed with the perfectly preserved bodies of the animals it has killed. The water is three to five times saltier than the sea, too dense to mix, and so starved of oxygen and loaded with hydrogen sulfide that a fish which wanders in is suffocated, poisoned, and chemically burned all at once. And yet the deadliest water in the ocean is surrounded by one of its richest gardens. At the edge of the poison, mussels and giant tube worms thrive in their thousands, feeding not on sunlight but on the methane and hydrogen sulfide leaking from the seabed. Through a process called chemosynthesis, bacteria turn that poison into food, and the animals farm them. It overturned one of the oldest rules in biology: that all life ultimately depends on the sun. We trace the whole story. How a lake can exist underwater, and why it comes down to salt and density. Where the salt came from: the ghost of an ancient sea that dried away in the middle of the Jurassic, more than 150 million years ago, then rose back toward the seafloor in slow domes of salt. Why the brine is so lethal, and how it preserves the dead so perfectly that crabs and fish lie intact for years. From there it only gets stranger. Cold seeps ring the planet by the thousands. Frozen methane, known as burning ice, sits on the seafloor in flammable mounds, with pale worms living on it. Certain tube worms anchored to the seabed today are over 250 years old, alive since before the United States existed. And the same conditions may exist on the icy ocean moons Europa and Enceladus, making a poisoned pool in the Gulf of Mexico the best preview we have of life elsewhere in the universe. The ocean keeps its secrets. This is Blues Below, where we explore the deep ocean's strangest mysteries, one story at a time. If you love deep-sea documentaries and the alien biology of the abyss, subscribe and come with us into the dark. Chapters: 0:00 The Jacuzzi of Despair 1:25 A Lake Inside the Ocean 3:15 The Ghost of an Ancient Sea 5:27 Why It Kills 7:37 Life at the Shoreline 10:14 The Methane World 12:37 Worlds Like This Sources: deep-sea footage courtesy of NOAA Ocean Exploration and the Okeanos Explorer, the Ocean Exploration Trust and E/V Nautilus, the Schmidt Ocean Institute, and MBARI. Brine pool and cold seep science draws on research by Erik Cordes of Temple University and colleagues, deep-sea tube worm longevity studies, and USGS gas hydrate work. Astrobiology context on Europa and Enceladus from NASA and JPL. Additional footage from public-domain and Creative Commons sources. #BrinePool #ColdSeep #DeepSea #OceanDocumentary #JacuzziOfDespair #Chemosynthesis #DeepOcean #MarineBiology #OceanScience #Europa #Enceladus #GulfOfMexico #Abyss #BluesBelow #UnderwaterLake