Hayate no Gotoku! Episode 18, title name as The Rare Card is Swimsuit (レアカードは水着です,Rea Kādo wa Mizugi Desu?) aired on July 29th 2007, the English Animax dub aired on July 6th 2009.
Hakuou academy is empty, due to summer vacation. A few of the students have taken a trip to the school's seaside camp. Hinagiku watches them leave, as she decided to stay behind because she doesn't like flying. Being his first time in such a jet, Hayate becomes sick, though Nagi manages to keep him calm. The Hakuou Three Amiga watch over the clouds below, and they ask Yukiji to come join them, but they mistakenly use the term kumo-umi to refer to the clouds, prompting Yukiji to remind them that it's actually unkai. She then says that she'll remember this for their kanji test, and they quickly panic, returning to their seats to write this in their notebooks. Himuro sits with Taiga, who was sleeping at the moment. He tries to get Taiga's attention , but he doesn't wake up. Himuro reaches over and increases the volume on his music player, causing him to quickly snap into action. Himuro asks him for a drink, and he runs off and gets Himuro cola. He returns with the cola, and Himuro quickly drinks it. He says that the drink was cold and delicious, getting Taiga excited. He sits down and puts on his headphones again, but Himuro asks him for seconds. Elsewhere, Kaede was relaxing, reading a magazine, while Koutarou was busy jogging around the jet. Koutarou asks him if he can sit down, but Kaede violently reminds him that he wasn't raising him to be a weakling. In fear, he quickly runs off, while Yukiji reminds Kaede to keep it down. At their seats, Hayate thanks Nagi for taking him along on this trip, but as he is doing so, his sickness gets the best of him and he vomits. Nagi reminds him that while he's sick, he shouldn't talk. In another part of the plane, Klaus and Tama are seen sleeping. The plane approaches Hakuou Island, Hakuou Academy's private island, where a man was waiting for them.
A slideshow of them unloading shows, intermixed with fanservice shots of Hinagiku, and then they're all seen riding a bus to the entrance, where a man named Schmidt hen Bach greets them and introduces himself as the butler and manager of the island. He declares that he intends to help everyone make their trip fun, and he starts by showing them all to their rooms: The Room of Greed for Yukiji, The Room of Idiots for the Hakuou Three Amiga, a room with a censored title for Taiga and Himuro, where a love bed awaits, The Room of Perseverance for Koutarou and Kaede, and The Room of Hikikomori for Nagi. Hayate says that he, along with Klaus and Tama, will go to the guest room, though Nagi wishes she was in the same room as Hayate. Yukiji announces over the PA system that everyone needs to get into their school swimwear and head to the pool. The girls (and Taiga) head to the pool in their school swimwear, and Koutarou joins them in ordinary swim trunks. The butlers and Tama sit off to the side, watching everyone. Yukiji tells the students to stretch before they swim, leading to another slideshow of fanservice images. Just when the lesson is about to start, a large mecha appears, which is revealed to be piloted by Schmidt. He announces that the mecha is the synchronized swimming controller machine. A quick shot of Hinagiku displays, and then the scene cuts to Schmidt in the cockpit of the mecha, where he pushes a skull-shaped button. This causes the mecha to launch several rays of light, which are revealed to be strings, with attach to everyone's wrists and ankles. In his attempts to create good memories, he drags them into the pool and forces them to swim to Power of Flower. They all protest this, and Hayate rushes to Nagi and asks her how she's doing, but Schmidt grabs Hayate also and forces him to join them. After the song finishes, Schmidt applauded all of them, but everyone involved was left miserable. Another of Hinagiku's fanservice shots shows, in addition to one of Sakuya's. Angry at his actions, Yukiji tries to punch Schmidt, but the lunch bell ringing stops her. He then announces that they'll have to change into new swimwear. He shows them the selection. As the Hakuou Three Amiga rushes in to check them out, he announces that he intends to create the selections for them. They turn around to see another large mecha held in the back of a large truck, which quickly launches and forces them into their new swimwear. Afterwards, a montage of their outfits is shown, though Nagi questions why Taiga is shown.
They start eating, and find the food to be delicious, but Schmidt introduces a special meal for them, which is a live white alligator. The alligator charges at them as they screamed. Meanwhile, the narrator mentions that Isumi got lost on her way to the seaside camp, and ended up in some snowy mountains, where she had collapsed. A St. Bernard comes to her rescue, and calls for someone else. In the city, Hinagiku ends up at a TurboGrafx competition, where she plays while a few people comment on the machine's limitations. Back at the camp, the alligator had gone on a rampage but eventually decided to leave, prompting Klaus to bid the alligator farewell and wish it the best, while Tama laid alongside him, with his stomach bulging. During their free time, the Hakuou Three Amiga are seen parasailing, Himuro and Tagia are cruising in a boat, Kaede is snorkeling in the depths of the water, and Tama and Klaus ride along on a jet ski. During this time, Hinagiku was also practicing Kendo. Nagi and Hayate were walking along the beach while the rest of them were playing. Hayate asks Nagi why she doesn't want to play, and she says that just spending time like this is the best. Yukiji was watching over everyone, and Schmidt brings her a drink, causing her to think that he actually is a decent butler when he isn't playing his usual tricks. Just then, a large whale appears, which swallows everyone to Yukiji's horror. Inside the whale, Schmidt says that he'll take them all on a deep sea outing, to their protest. Still on the beach, Hayate and Nagi watch over the entire scene, and just decide to walk away Meanwhile, at an apartment building, Ayumu is seen working on a crossword puzzle, while eating snacks. Later that evening, Schmidt sits them down for a dinner, but everyone is in a state of gloom from his actions. Eventually Izumi stands up and protests their actions, getting the support of the rest of the three girls. Yukiji joins them, as she doesn't like being used as his entertainment. Eventually, everyone else decides that they've had enough, and they decide to head home. Everyone was about to leave, but Schmidt has his maids and butlers reveal their true forms, as various monsters. Hayate springs into action to protect Nagi, and he swiftly exterminates some of the horde. Weak as ever, Koutarou relies on Kaede to fight, but Kaede pulls out a controller, causing a pit to form in the ground underneath Koutarou, where he falls right into a pit of monsters. Himuro knocks out a few enemies, but one was about to get the upper hand on him. Just then, Taiga rushes in and aggressively throws rose petals at it, causing it to stumble, opening it up for an attack from Himuro. Klaus used some insectiside to eliminate some of the monsters, while Tama just sets up a mosquito coil. Frustrated by his attempts to create "fun" memories, Yukiji ends up knocking out Schmidt with a large hammer. Afterwards, they all head back to the jet, where they start flying home, but everyone quickly notices that they're flying over mountains. Yukiji heads to the cockpit to tell ask the pilot where they're going, but the pilot turns out to be Schmidt, who tells her that since they didn't like the seaside camp, he'll create a camp in the woods next.
Before the episode ends, a short sequence named Maria's Room plays, where she interviews Sakuya's butlers Makita and Kunieda. Since they hadn't appeared in any episodes recently, she asks them what they do on their days off. Makita says that he had bought a guitar, while Kunieda says that he was reading books and cleaning up his room. Maria thanks them for taking the time to do this, and she asks the viewer to return for the next episode.
The private jet used to take the Hakuo Academy students to the school's seaside camp is a parody of the Pokémon Jet.
Inside the "greed room" Schmidt escorts Yukiji to, a blue stuffed animal heavily resembling Cerberus (also known as Kero) from Cardcaptor Sakura is seen on a couch.
Inside the "room of idiots" Schmidt escorts the Hakuo Three Amiga to, a pink stuffed animal heavily resembling Ah-kun from Moetan is seen.
Before Schmidt forces Hayate, Nagi, Yukiji, Koutarou, Taiga and the Hakuo Three Amiga to do synchronized swimming, he is seen piloting a mecha heavily resembling Zambot 3 from the series Invincible Super Man Zambot 3.
During the scene where Schmidt is changing everyone into their swimsuits, the mecha he is using resembles the Lancelot from Code Geass. In particular, its appearance in the back of a truck resembles the scene when it was first launched.
Additionally, the same mecha Schmidt is using has a color scheme similar to the Nirvash, from the anime series Eureka Seven.