The place where this submarine disappeared is in the Atlantic Ocean near Canada. Look at the map. 600 km away from Newfoundland, a Canadian island. At this place, in the depths of the water, you will find the wreck of the Titanic, broken into two parts. The bow and the stern both lying about 800 meters away from each other.
The Titan submarine that disappeared here was not a submarine but a submersible. These two words are very similar to each other. So, till now, we was using the word submarine to simplify things, but there is a very important difference between these two words.
Submarines have their own power. They can use a port to go into the sea and come out of the sea independently. But submersibles cannot do that. To launch a submersible into the water and for it to come back, a support ship is needed. A ship that is present on the surface of the water and is controlling everything.