The deeper the Titan goes under the water, the greater the pressure on the wall vessel of the Titan.
Liquid pressure P = ρgh
Liquid pressure = density of water x gravitational field strength x height of water before water surface
Inside the vessel, the pressure is maintained at about atmospheric pressure for the crews to breathe normally, just like on sea level or on ground.
Due to the huge pressure difference between outside and side, the Titan will implode when the hull of the vessel is not able to withstand the pressure.
Deepest condolences to the crews…
https://www.straitstimes.com/world/titan-submersible-what-is-a-catastrophic-implosion
Evan's Space 