It seems it has over half a dozen mechanisms to return it to the surface, including a final failsafe weight that releases on a timer after 14 hours, so there is reason to hope its surfaced, but there are innumerable ways for this thing to go south.
Terrible situation, but very unnecessary. I get that this company are saying they're using billionaire money to fund some scientific research but it feels a tenuous link for a thrill seeking/bucket list exercise with colossal risk.
The whole thing has now been mapped, digitised and is now constantly degrading.
I can't help thinking the site should be left in peace without significant scientific justification to go there.