Answer: Hypersaline, oxygen-deprived lakes on the seafloor
Notes: Scientists discovered deadly brine pools beneath the Red Sea that kill or stun marine life. Brine pools are hypersaline, oxygen-lacking lakes on the seafloor, denser than surrounding ocean water. They are also called "underwater lakes" because their high salt content prevents mixing with seawater. The Orca Basin in the Gulf of Mexico has the deepest known brine pool, 2,200 meters below sea level. This pool is 8 times saltier than the Gulf, with a salt content of 300 g/liter. Most sea life cannot survive in these pools, but some specialized organisms thrive.
