At the time of The Flood it was decided that the koi Carp deserved their own ark so Noah built one with a few levels allowing the Koi to swim freely up and down. It had to be towed behind the main ark on a very long rope. They needed the protection of their ark but also deserved some freedom so the koi would sometimes go off on a little adventure and when they came back they would tell Noah where they'd been and what they'd done.
Noah looked forward to this and day after day there was a new story for him.
This was probably the very first multi-storey carp ark.