# Dead Pools (DD-049) > Brine pools are lakes on the seafloor: pockets of brine so dense they don't mix with the seawater above, complete with shorelines and even waterfalls. They form where seawater dissolves salt deposits buried under the seabed, such as the layers left when the ancient Gulf of Mexico evaporated, or the evaporites of the Red Sea rift. The best-known example, the Gulf of Mexico's 'Jacuzzi of Despair', lies about 1,000 m down and is about 30 m around. Its brine runs 80 to 110 psu (normal seawater is about 35). It's warm, nearly oxygen-free and charged with methane and hydrogen sulfide. Crabs, isopods and fish that wander in die, and their bodies are preserved along its rim. - Department: Nature (also Dark Facts) - First published: 2026-01-19 - Last updated: 2026-01-19 - Permalink: https://detailenjoyer.com/case/dead-pools/ - Author: Marcus Easterling (DetailEnjoyer), The Detail Department ## On the timeline - **Millions of years ago**: Evaporation of a shallower Gulf of Mexico leaves the thick salt layers that feed today's brine pools Full timeline: https://detailenjoyer.com/timeline/?case=dead-pools ## Quick facts - **DD-049-F01**: The Gulf of Mexico's 'Jacuzzi of Despair' is a lake on the seafloor, about 1,000 m down, four to five times saltier than the ocean around it. _(Write-up · Exhibit C (How salty))_ - **DD-049-F02**: Animals that stray into seafloor brine pools die from the salt, low oxygen and toxic gases, and their bodies are preserved along the rim. _(Write-up · Exhibit B (Where the salt comes from))_ ## Write-up There are lakes at the bottom of the sea. Some are four to five times saltier than seawater, with little or no oxygen. 1. **Lakes under the sea**: Brine is so much denser than seawater that it pools on the seabed with its own shoreline. The Jacuzzi of Despair is a crater-like pool that rises 3 m above the seafloor and spills brine over one edge in a 'waterfall'. 2. **Where the salt comes from**: Millions of years ago the Gulf of Mexico was shallower, and evaporation left thick salt layers that were later buried. As those layers shift and crack, seawater dissolves the salt, and the brine collects on the seafloor along routes also used by rising oil and gas. 3. **How salty**: The top 3 m of the Jacuzzi of Despair measured 80 to 110 psu, about four to five times saltier than the surrounding ocean (about 35 psu). Beneath it was hydrocarbon-charged fluid mud at 19 °C. 4. **What makes them deadly**: It isn't only the salt. The brine has little or no oxygen and is rich in methane and hydrogen sulfide. 5. **Pickled remains**: Researchers found dead isopods and crabs preserved along the pool's edge. In the words of Woods Hole scientist Scott Wankel, creatures that fall in 'die and get pickled and preserved.' 6. **Bottomless**: A sensor lowered about 19 m into the pool never reached a hard bottom, and methane bubbles were seen rising from inside. ## Related case files - [Offshore Oil (DD-033)](https://detailenjoyer.com/case/offshore-oil/): The same Gulf of Mexico salt and hydrocarbons. - [Heavenly Lake (DD-019)](https://detailenjoyer.com/case/heavenly-lake/): A very different kind of lake. - [Death Foam (DD-043)](https://detailenjoyer.com/case/death-foam/): Another way animals die from lack of oxygen. - [Foreverest (DD-063)](https://detailenjoyer.com/case/foreverest/): Another place where the dead stay where they fell: more than 200 climbers' bodies are thought to remain on Everest. - [The Glacier That Bleeds (DD-725)](https://detailenjoyer.com/case/the-glacier-that-bleeds/): Another ancient brine, this one pouring out of an Antarctic glacier and turning red in the air. - [Danakil Depression (DD-055)](https://detailenjoyer.com/case/danakil-depression/): Brines so extreme they're deadly: seafloor brine pools that kill animals that fall in. - [Chicxulub Crater (DD-693)](https://detailenjoyer.com/case/chicxulub-crater/): Another case under the Gulf of Mexico ## Reel vs. record - **Confirmed from the frames**: the Reel is about seafloor brine pools (captions at 0.8–2.4 s). They're dense, have sharp shorelines and are deadly to animals that fall in. [Oceanography 2016; CSM] - **Incomplete**: the Reel blames salinity alone, but the brine also has little or no oxygen and carries methane and hydrogen sulfide. [VOA; Discovery] - **Vague**: 'salt-rich fluids seep out of the Earth's crust.' More precisely, seawater dissolves ancient buried salt layers (in the Gulf of Mexico, left by an evaporated shallow sea), and the brine rises along cracks with oil and gas. [Discovery; Oceanography 2016; CSM] - **Confirmed with numbers**: 'several times higher' salinity. The Jacuzzi of Despair measured 80 to 110 psu, about four to five times seawater's 35. [Oceanography 2016; CSM] - **Footage note**: the Reel doesn't name a site. Its opening pool with a shoreline and the crab beside the brine look like Gulf of Mexico survey imagery, but that's unconfirmed. [frames] ## Video: Dead Pools: There Are Lakes at the Bottom of the Sea - Duration: 21.7 s · Published: 2026-01-19 - File: https://detailenjoyer.com/assets/videos/DTs-FLJEdn4.mp4 ### Transcript DID YOU KNOW? Underwater brine pools are extremely salty, dense bodies of water that form on the seafloor when salt-rich fluids seep out of the Earth's crust and settle into depressions, creating sharp, visible boundaries surrounding seawater. Because the salinity is several times higher than normal ocean water, these pools are toxic to most marine life, causing fish and other animals that fall in to become stunned or die. NOW YOU KNOW! ## Questions & answers **Q: Why doesn't brine mix with the seawater above it?** A: It sits on the seabed with its own shoreline. _(Source: Write-up · Exhibit A (Lakes under the sea) · Wankel et al., ROV Hercules Investigates Brine Lakes on the Bottom of the Ocean (Oceanography, 2016); How this 'Jacuzzi of Despair' formed beneath the Gulf of Mexico (Christian Science Monitor, 2016))_ **Q: About how much saltier is the 'Jacuzzi of Despair' than the surrounding ocean?** A: It measured 80 to 110 psu vs about 35 for seawater. _(Source: Write-up · Exhibit C (How salty) · Wankel et al., ROV Hercules Investigates Brine Lakes on the Bottom of the Ocean (Oceanography, 2016); How this 'Jacuzzi of Despair' formed beneath the Gulf of Mexico (Christian Science Monitor, 2016))_ **Q: Where does the Gulf of Mexico's brine salt come from?** A: Seawater dissolves the salt as the layers crack. _(Source: Write-up · Exhibit B (Where the salt comes from) · The Jacuzzi of Despair Is a Deadly Lake Within the Gulf of Mexico (Discovery); Wankel et al., ROV Hercules Investigates Brine Lakes on the Bottom of the Ocean (Oceanography, 2016); How this 'Jacuzzi of Despair' formed beneath the Gulf of Mexico (Christian Science Monitor, 2016))_ **Q: Besides salt, what makes brine pools deadly?** A: Animals that fall in suffocate in a toxic chemical soup. _(Source: Write-up · Exhibit D (What makes them deadly) · 'Jacuzzi of Despair' Found in Gulf of Mexico (VOA News, 2016); The Jacuzzi of Despair Is a Deadly Lake Within the Gulf of Mexico (Discovery))_ **Q: What did scientists find along the Jacuzzi of Despair's edge?** A: The brine 'pickles' animals that fall in. _(Source: Write-up · Exhibit E (Pickled remains) · Wankel et al., ROV Hercules Investigates Brine Lakes on the Bottom of the Ocean (Oceanography, 2016); 'Jacuzzi of Despair' Found in Gulf of Mexico (VOA News, 2016))_ ## Sources - [Wankel et al., ROV Hercules Investigates Brine Lakes on the Bottom of the Ocean (Oceanography, 2016)](http://hdl.handle.net/21.11116/0000-0001-C34B-F) - [How this 'Jacuzzi of Despair' formed beneath the Gulf of Mexico (Christian Science Monitor, 2016)](https://www.csmonitor.com/Science/2016/1102/How-this-Jacuzzi-of-Despair-formed-beneath-the-Gulf-of-Mexico) - ['Jacuzzi of Despair' Found in Gulf of Mexico (VOA News, 2016)](https://www.voanews.com/a/mht-jacuzzi-of-despair-found-in-gulf-of-mexico/3576459.html) - [The Jacuzzi of Despair Is a Deadly Lake Within the Gulf of Mexico (Discovery)](https://www.discovery.com/exploration/Jacuzzi-of-Despair-Deadly-Lake-Gulf-of-Mexico) - [Brine pool (Wikipedia)](https://en.wikipedia.org/wiki/Brine_pool) ## Cite this case file Easterling, Marcus. "Dead Pools." The Detail Department (DetailEnjoyer), case file DD-049, last updated Jan 19, 2026. https://detailenjoyer.com/case/dead-pools/