Water Rats are talking beasts in Narnia.
They are intelligent creatures and excellent swimmers, which can swim in lakes or rivers around the world of Narnia.
At the very beginning of Narnia, Water Rats were present at the coronation where Frank I and Queen Helen become the first King and Queen of Narnia.
One Water Rat was able to affiliate the Calormenes, which he did by operating a small punt with a pole. This occurred during when the Calormenes began felling the Narnian trees at the end of the Narnian world.