What is in this image? Describe it as if you were explaining it to someone from the 15th century.

Behold a curious drawing featuring a fantastical creature, akin to a child or a small woodland sprite, seated atop a great fish as it swims through the water. The creature perched on the fish bears semblance to a rabbit, with oversized ears and fluffy tail, but its face is gentle and human-like, with an expression of delight and adventure. The fish, mighty in size, moves briskly causing spray of water around it, vividly captured even in this simple rendering. Such fantastical depictions serve not only to entertain but to ignite the imagination about the remarkable and the supernatural, a concept well appreciated even in our era.