You cannot be serious. “A familiar face”? So just merrily go through the remains of the cabin with a robot and see if you can see someone who looks like Uncle Pierre or Aunt Marielle?
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.