[pezdeath]

How big of a ship would you need to even hold that tether?

At 4000m under the ocean, you'd need like 10000m of cabling at a minimum I'd assume? And then you'd need the tether + winch to be capable of supporting and lifting the sub at that depth.

I'd be amazed if any country let alone company has that capability outside of maybe the US military.

[UniverseHacker]

I think a 4mm dyneema line would have been more than sufficient to pull this to the surface in an emergency, and would have been relatively cheap and light. It could safely 1-2 tons of force, which would rapidly lift a neutrally buoyant sub of any size…

This would cost about $3/meter.

[SirMaster]

How do they control the unmanned subs that they use to survey the Titanic then?

They are not tethered?

[cududa]

A data link tether and one capable of pulling up a giant heavy craft are very very different