Gulf of Mexico

A brine pool, 1,000 meters below the gulf’s surface, was discovered in 2014.

An excerpt from the article 26 facts about Gulf of Mexico
It is 3,7 meters deep, with a circumference of 30 meters. Its salinity is about five times higher than the rest of the water, and thus it is unable to sustain any form of life, apart from bacteria, tubeworms, and a few kinds of shrimp. It is known as the Hot Tub of Despair.