[Sam (Winchester) was making his way from the Athletic Center to the great wide elsewhere of the dome when he heard the sound of hoof beats. It's not really the sound you expect to hear in an underwater prison. Then again as strange as it is, it's not that strange when you consider this underwater prison also has stables in that very sector. Still, even after five months in Marina(s)—a place that makes his home life seem relatively normal—he has enough "check out the strange" instinct left in him to go do just that.
He makes it in just enough time to see the mystery horse run into the water and come up as a very unclothed Sam Merlotte.
That was not the strange he wanted to see. Beaches should really have more cover...for both of them because he's pretty sure he's going to be spotted, and he doesn't even know what to do with a...werehorse?]