The Laurentian Abyss is estimated to be 19,685 feet deep, which is approximately 3.7 miles. It is an underwater depression located off the eastern coast of Canada in the Atlantic Ocean. Researchers consider it less of a trench and more of an underwater valley.
The Laurentian Abyss has hydrothermal vents that produce an ecosystem that doesn't need sunlight for survival. The underwater depression was used in the plots of the movies "The Hunt for Red October," "Transformers" and "Transformers: Revenge of the Fallen." The latter two movies incorrectly stated that the abyss was 55,800 feet deep, which is approximately 10.6 miles.