Pollywhale are a species of animal that resemble a cross between a tadpole and a whale. With the legs and tail of the former, but colors and fins reminiscent the later, Pollywhales can be seen in the canals of Balancoire.
For the Animal Collecting quest in Baten Kaitos: Eternal Wings and the Lost Ocean, Kalas can acquire a Pollywhale in the canal they're often seen swimming about in in Balancoire.