The deepest point in the ocean is referred to as the Challenger Deep.
Mariana's point and oceanic limit are not associated with the deepest point of the ocean.
The Mariana Trench, located in the Pacific Ocean, is the location where the Challenger Deep can be found. It is the lowest point, or the deepest part of the trench, and is said to be approximately 36,070 feet (10,994 meters) deep.
Therefore, if you're looking to refer to the deepest part of the ocean, you would refer to it as the Challenger Deep.