While On A Trip, Their Dog Took Them To An Abandoned Boat Which Hid The Impossible Underneath

Upside Down

Pluto reached the middle of a river, where there was a boat lying upside-down. There was nothing else around and nor were there any traces of a human close by. What made Pluto run this far was something all wanted to know. When they tried to take Pluto back, she refused. Why?