- "I've had a few run-ins with this 'un, he's a mean-spirited an' bad-tempered ole watervole."
- ―Orkwil Prink
The unnamed Grumpy Watervole was a mean-tempered, unkind watervole who lived along one of the River Moss's tributaries.
After Orkwil Prink was banished from Redwall Abbey, the watervole refused to give the hedgehog food or drink, aimed an arrow at him, and tricked him into doing subservient tasks before sending him into the wilderness.
Later, the watervole was attacked by a pair of rats. Orkwil saved him and bound the vermin to a tree, showing the opposite of the watervole's contempt for him. The watervole later revealed that he tossed the two rats into a swamp, still bound, and weighted with stones.
He was captured by the crew of Vizka Longtooth and used as bait for the Redwallers. The watervole was knocked out cold by Benjo Tipps, repeatedly insulted, forced to answer questions from Rorc, threatened by Orkwil, and knocked aside by Gorath.
He was extremely paranoid of the Sea Raiders discovering him within the Abbey. After being exiled by Benjo, the watervole stole The Sword of Martin, killing Sister Atrata in the process. However, he stole the sword because Orkwil had stolen his dagger.
Though the watervole never appeared to do anything good or kind, he was seemingly mistreated and abused by everyone he met.