The tether is not connected directly, it's connected to a TMS that then has a smaller cable connected to the submersible. Ex. https://www.researchgate.net/fig

The tether is not connected directly, it's connected to a TMS that then has a smaller cable connected to the submersible. Ex. https://www.researchgate.net/figure/Schematic-image-of-a-working-class-ROV-TMS-system-during-deep-water-deployment_fig1_361242757 https://www.researchgate.net/figure/Schematic-image-of-a-wor... https://f-e-t.com/subsea/vehicles/tether-management-systems/ https://f-e-t.com/subsea/vehicles/tether-management-systems/ There's also this one which looks like it can get to the depths of the Titanic: https://nautiluslive.org/tech/rov-argus https://nautiluslive.org/tech/rov-argus So it was certainly possible to do this with a tether, but it would have been much more expensive.