Imagine being on a merchant ship in medieval times, sailing your route. You look off the poop deck and you see a giant rabbit head. WTF? yah a giant sea rabbit. Aw how cute. NOPE! Next thing you know your ship is torn in half and your crew is eated. Sounds like something off monty python.
The Sea Hare!!!
Seriously who comes up with this shit? Impossible, that's how you know it's true. We know less about our oceans then we do about space.
What the encyclopedia tells us about the monster:
This is the name given to a sea monster in the traditions and beliefs of medieval Europe. It was described as having the body of a fish but with the legs, head, and ears of a hare, behind which were fins. It was said to be a predatory creature that would attack almost any living thing within it's reach, pursuing those that were not. The description comes from a time when travelers and sailors described and exaggerated, the creatures that they encountered, and also when people generally believed that what existed on land also had its counterpart in the oceans and skies.*
Even though it wasn't described as a giant rabbit-fish, I don't care. The thought of having a little aggressive gar-fish like rabbit swimming around is pretty scary, but way worse when he can tare your little sail boat in half.
*Giants, Monsters & Dragons. An Encyclopedia of Folklore, Legend, and Myth. By Carol Rose.