they are the ghosts of the fur coat! no wonder it swam to collapsible AThere is still some discrepancy about this. Although Mr & Mrs Spencer are quoted as being the occupants of Cabin B-78 in most sources, The Cave List has them in B-76. Furthermore, Etches would in all probability have known in which cabin the Spencers were and if they were indeed in B-78, would he not have remembered the fact later? The fact that Etches did not appear to know the occupants of B-78 - those who talked to him through the closed door - might mean that he already knew that the Spencers had left their cabin, which then might have really been B-76 as per the Cave List.
If that was the case, the question remains as to who was in B-78 when Etches knocked on the door.