Merrily or sadly, but these robots don’t sound like big lumbering things. Probably something about the size of a catfish that runs on batteries and sonars its data (or an abridged version of it) back out with no need for a tether. One coordinated visit with photos of all faces would do if the remains are sitting stably on the ocean floor.
>>One coordinated visit with photos of all faces would do if the remains <<
That might be fine for unconnected analysts but that’s not the memory you want to leave with close relatives. I am sure their ride to the bottom was not smooth. Quite a few probably got the snot knocked out of them with overhead luggage slamming into them and so on and so on.