One day at school, Sunset Shimmer's empathy powers get so out of control that she starts hearing others' thoughts without touching them, and she discovers her friends are experiencing the same thing. As they wonder why, Rainbow Dash zooms in with her super speed, bragging about using her powers to do everything. Twilight theorizes that, because their magical geodes are connected, the more each of the girls use their powers for everyday tasks, the more they get supercharged. So they agree to use their geodes in moderation. When Zephyr Breeze enters and asks Rainbow out on a date, Rainbow is about to use her super speed to run away, but her friends warn her not to, and she simply walks away from Zephyr. Later, Sunset's powers return to normal.

Twilight is excited about her upcoming date with Timber Spruce at the planetarium, which she insists is merely a "hang-out". She has the entire evening planned out, and Fluttershy gives her something special for the occasion: a jar of bugs. At the planetarium, Twilight and Timber start their evening together, but all of Twilight's planning ends up being in vain: the exhibit on gravitational fields has been removed, the planetarium show has been canceled, and the sky is overcast with clouds, preventing them from seeing the stars and constellations with the telescope. Twilight is disappointed that she wasn't able to impress Timber, and Timber is equally disappointed about not being able to impress her with his new knowledge on astronomy. When Twilight lightly kicks her backpack, the bugs in the jar Fluttershy gave her fly out, revealed to be fireflies, and they light up the night by forming the constellations. Starstruck, the two spend the rest of the evening looking at the fireflies.

During her fashion internship at Prim Hemline's boutique, Rarity is tasked with designing a new window display for a visiting Fashion Week style scout. Unfortunately, the pressure starts to get to her, and she confides in Sunset Shimmer. As they walk through the city, they come upon some graffiti drawn by a mysterious and popular street artist named "Flanksy", and Rarity gets inspiration. Later that night, she is dissatisfied with her finished work, but Sunset gets an idea. The next day, Rarity returns to the shop and sees a crowd of people impressed by the now improved window display, including Prim Hemline. Looking behind her, Rarity sees Sunset in an alleyway with paint on her cheek and realizes that Sunset is in fact "Flanksy".

While playing a game on her smartphone at the beach, Sunset Shimmer discovers a message in a bottle. She shows it to Twilight and Pinkie Pie, and they realize it's a treasure map that looks like the beach they are on. When they follow the map to a treasure chest under the pier, they discover a second message in a bottle that's encoded and a decoder ring. Sunset decodes the message using the decoder ring, and it tells them to follow a trail of seashells to an "X" at "the end of the rainbow". The "rainbow" in question is revealed to be an ice cream truck, and the "X" turns out to be a Rollin' Sushi Truck. The sushi truck attendant congratulates the girls on solving their promotional treasure hunt, for which they win sushi at a discounted price. The girls are a little disappointed at not finding real treasure, but they enjoy the sushi anyway.

Twilight, Pinkie, and Rarity prepare to go sailing at the beach, with Twilight having memorized a nautical dictionary just for the occasion. Rarity overpacks for the trip, and Twilight is forced to leave her luggage behind due to the extra weight on the boat. When the sea winds carry the boat in the wrong direction, Twilight guides her friends in correcting their course, but the turbulent waters cause her to lose her map. As the boat heads on a collision course with a large rock, Pinkie uses her geode powers to create a wave that brings the boat back to the pier. With the three girls soaked, Rarity produces some towels, and they share a laugh over their exciting adventure.

Rarity interrupts Applejack and Rainbow Dash in the middle of their lounging on the beach and tells them she lost one of her one-of-a-kind earrings. Applejack and Rainbow agree to help her find it, and she supplies them with some metal detectors. Rarity, Applejack, and Rainbow spend all afternoon looking for Rarity's missing earring, but all they find is a variety of other lost beach junk. Rarity apologizes for wasting her friends' day, but they've enjoyed the thrill of discovering things under the sand. When Rainbow Dash sees how distraught Rarity is over her lost earring, she uses her super speed to look through the pile of junk one more time. She finds an earring, but it's not the one Rarity lost. Rarity thanks her friends for their help and decides to do one more search with the metal detector. Just then, she discovers her earring was never missing—it had gotten tangled in her hair, much to her embarrassment.

As Fluttershy and her friends organize an adoption for all the crabs on the beach, Pinkie Pie decides to get some shaved ice for them. On her way back from the shaved ice truck, Pinkie gives one of her cones away to a little boy who accidentally drops his on the ground, and another gets snatched by a seagull. In order to get across the hot beach sand, Pinkie rolls on a beach ball, jumps across beach umbrellas, and sails on a kite before returning to her friends. As the crabs get irritable from the heat, Pinkie gives them her last shaved ice cone so they can cool down. With no cool treats left, Rainbow Dash zooms over to the shaved ice truck to buy a second batch.

Rainbow Dash and Applejack invite Fluttershy to go surfing with them, but she doesn't know how to surf. Her brother Zephyr Breeze suddenly arrives, bragging to Rainbow about being a long-time surfer, but Fluttershy knows for a fact he is lying. When Rainbow and Applejack invite him to show them his surfing skills, he instantly loses much of his confidence but joins them anyway. Out on the waves, Rainbow and Applejack surf with ease, but Zephyr wipes out almost immediately. Back on the shore, he admits he actually doesn't know how to surf, and he begs Rainbow Dash for forgiveness and surfing lessons. Begrudgingly, Rainbow agrees to give Zephyr some pointers.

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.

Pinkie Pie picks up a magazine Rarity left behind on her beach chair and finds a "best friends" quiz inside, and she decides to take the quiz with Twilight. Unfortunately, they keep coming up with the wrong answers to questions such as "What is your best friend's favorite food?" and "What is your friend's biggest fear?", and they both score a zero. Unable to accept the idea of failing a test, Twilight decides to run her own equations to prove that she and Pinkie are best friends. After several hours of writing equations in the sand, Twilight finally comes up with the answer, but the ocean tide washes her equations away. Pinkie fears all of Twilight's work was for nothing, but Twilight tells her their friendship cannot be measured by numbers.

Applejack is the substitute lifeguard on duty at the beach. Usual lifeguard Timber Spruce tells her lifeguard duty is typically uneventful, but Applejack resolves to be prepared for anything. When someone cries out for help, Applejack is the first to respond. When someone else gets in trouble, Timber Spruce springs to action so that Applejack doesn't make him look bad. This turns into a light competition between the two to see who can respond to trouble the fastest. When Bulk Biceps cries out for help in the water, Applejack and Timber both swim out to save him, but they pull him in opposite directions. Bulk starts to cry, not wanting to see Applejack and Timber fight. The two lifeguards realize their competition has been silly and that they actually make a good team, and they pull Bulk to shore together. Their determination to save people on the beach thus turns more friendly than competitive, much to Bulk's joy.

It's the last day of school at Canterlot High, and while Rainbow Dash is excited, Twilight is dismayed. Four hours before the last school bell, Twilight tries to get in as much extra credit work as possible and write thank-you letters to all of her teachers. Meanwhile, Rainbow Dash wants the school day to be over as soon as possible. In their last class of the day with Miss Cheerilee, Rainbow Dash convinces her to play a Daring Do movie during class. Throughout the movie, Twilight rushes to finish her extra credit projects, and Rainbow Dash keeps looking at the clock. When the bell rings, Twilight wails in despair over not finishing her projects. Fortunately, Rainbow Dash points out that she can read anything she wants during the summer and even go to the library. Twilight's mood instantly turns around, and she is excited for summer vacation.

At the Canterlot Animal Shelter, Fluttershy sets up a camera to shoot an adoption commercial for the shelter animals. As soon as she finishes setting up, however, she gets nervous at the thought of hundreds of people watching her on TV. This nervousness causes her to film several bad camera takes. Changing her approach, she decides to film the animals from behind the camera, but the animals act rowdy and unpredictable all throughout her filming. When Twilight and Applejack arrive later, Fluttershy loses all hope for making a good commercial. But after seeing the footage she already took, Twilight and Applejack tell her she perfectly captured the fun of having a pet. With a little editing, Fluttershy finishes making her commercial.