Pinkie Pie, Twilight Sparkle, Sunset Shimmer, and Fluttershy take a selfie at the beach, and Twilight notices a black splotch in the photo's background. Sunset and Pinkie believe it to be a sea monster, but Twilight and Fluttershy are more skeptical. They each decide to do their own investigations into the matter. 

Twilight views the ocean from the lifeguard stand, accompanied by Timber Spruce. Just as Sunset and Pinkie approach the ocean, Pinkie realizes she doesn't have her floatie. Suddenly, something rises out of the water and approaches the shore, and even Twilight and Timber begin to believe it is a sea monster. It turns out to be Fluttershy, and she reveals the true identity of the "sea monster": Pinkie's missing floatie.