Grolon rat
From Tardis Wiki, the free Doctor Who reference
We don't know the name of this thing.
But we do know where it came from. So we're using that to title the page logically. If you know a better, more precise name, tell us.
Grolon rats were a type of dangerous creature from Grolon which could swim. In 2009, a pack of Grolon rats slipped through the Cardiff Space-Time Rift and infested Butetown. They attacked an angler, stripping him to the bones. (PROSE: The Undertaker's Gift)