Do we know if they were going to be ending the tenancy voluntarily or if they had been served with a notice to quit (NTQ)? It is possible that if a notice had been served, they possibly had not left on the day they were supposed to. The landlord will obviously know if it was them ending the tenancy or him ending it. If one phone was left at home and one taken with them, if there was an intended plan to enter the water voluntarily, is it possible that only one of them knew this? Could this account for the scream? One of them wants to enter the water, is it possible the other one did not know this was about to happen, screams were heard? Could they swim, did one go in to help the other?