Looks like we're in a lot of luck :-/. The warm water heater has been submerged by the flood and refuses to work. Since the sewer contents have probably touched the interior of the heating machine, there's a high probability it's broken.

The landlord came by and contacted their insurance assistance service. They are sending someone over this afternoon to evaluate the situation. Let's cross our fingers since it's already clear that the landlord would have a lot of trouble to free the funds needed to install a new heater in a short notice.