Have a robot grab a bit of a body with a familiar face for a DNA test to compare with living relatives, I suppose. Or compare to photographs taken when the person was living. Being doused in salt water of that strength would probably preserve features pretty well, just like well-packed pickles.
IMO, the top priority should be retrieving the wreckage (whether or not bodies are in it)in order to determine what caused this awful crash and hopefully preventing future ones in like circumstances. The bodies could yield clues as well - spine compression and arm/leg fractures could provide clues as well. We know what injuries the previously recovered individuals sustained, but if people’s injuries varied by seat location, it might say something about whether the aircraft broke up before it hit the water.
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?