Yo, Ho, Ho! Go, Popplio! (Japanese: アシマリ、がんバルーン！Ashimari, Give it Your bALLoon!) is the fifth episode of the Sun & Moon series, and the 944th episode of the Pokémon anime. It first aired in Japan on December 1, 2016, in Canada on April 15, 2017, in the United Kingdom on April 18, 2017, and in the United States on May 15, 2017.
Ash’s class is going on a fishing trip, and Professor Kukui asks Lana to be in charge! Everyone casts their lures, with varying results—Lana befriends one Pokémon after another, but Ash and Mallow can’t get the timing right, Sophocles is too busy collecting data, and Lillie hooks a magnificent Milotic that gets away when she freezes.
When they take a break, all their new Pokémon friends get scooped up in a Team Rocket net—and then find themselves falling toward some rocks! But Lana’s Popplio has been working hard for such an occasion, and it creates a giant water balloon to cushion the fall and save the day!
Ash heads out for school early as Pikachu and Rockruff play. On their way to school Ash spots Lana and Popplio testing their balloon skills. They continue as Ash goes on ahead to school. Arriving at school, Ash is surprised when a sleeping Rowlet falls out of his bag. Later Professor Kukui informs his students that tomorrow's extracurricular lesson will involve connecting with sea Pokémon which will involve going fishing. Outside Team Rocket are spying on them and wonder what Ash is doing going to school when they are spotted by Samson Oak, who states that they seem suspicious, but Team Rocket claims that they are just tourists. Back in class, Professor Kukui tells Lana she will be in charge of the lesson. Later Ash and Lana are walking home with Lana offering Ash one of her fishing rods when Lana decides to show Ash one of Popplio's techniques unaware that Team Rocket are spying on them. Down on the beach, Rotom provides data on Popplio which includes making balloons.
Ash realizes that this was what Lana was doing that morning. Lana explains that she met Popplio here when it was being attacked by several Team Skull Grunts but she soon dealt with them. After Popplio was treated by Nurse Joy, Popplio agreed to be her partner. Popplio manages to make several balloons but they are small and quickly pop. Lana explains her dream is to make the biggest balloon possible to make her spend more time underwater. Another balloon attempt results in a bigger balloon which flies away before popping. Spotting Lapras excites Ash as Lana explains that it is her Ride Pokémon. Overhearing this, Team Rocket decided to capture as many Ride Pokémon and Meowth decides to come up with a plan. Inside Lana's house, Ash meets Lana's sisters Harper and Sarah who excited to see Pikachu. They take him into the next room to play which starts to bother Pikachu. Lana tells them to stop and they see Ash and ask if he is her boyfriend which Lana denies. Their antics annoy Pikachu which results in him shocking everyone.
The next morning, the class gather where Lillie wears a protective suit. Professor Kukui hands over teaching duties to Lana and despite being nervous begins the lesson. The class get on the Lapras and Wailmer who take them to their fishing spot. Lana begins her lesson by saying that many marine Pokémon live here and they cast their lures into the water as Pikachu dips his tail in. Lana instructs the class and the best course of action before managing to reel numerous Pokémon. Ash and Mallow soon get bites but their reactions aren't enough to reel it in successfully. Kiawe hasn't caught anything as Sophocles isn't keen on the others distracting. Pikachu gets a bite on his tail which ends up being a Magikarp. Pikachu flicks Magikarp and it lands in Ash's hand but it splashes and goes back into the water. Lillie gets a bite which turns out to be a Milotic and tries to reel it in. Lana and Ash rush to help Lillie with Ash leaping across the water only to be hit as Milotic jumps out of the water sending him into the water as the line snaps as Professor Kukui decides the time has come to take a break.
They take their break on a small island where Professor Kukui gives them 15 minutes to relax. As the Pokémon play, Team Rocket swoop down in their balloon and capture the Ride Pokémon along with several others. Team Rocket start to leave but Jessie notices the extra Pokémon. Their actions annoy Lana as Ash tells Pikachu to attack, only to be stopped when Team Rocket points out that the the Pokémon will be hurt. Ash comes up with another plan and has Pikachu jump on Rotom to gain some momentum. This allows Pikachu to fly towards the balloon and break through the net. Lana gets Popplio out to make a large balloon which allows the Pokémon bounce off and land safely in the water. Team Rocket aren't happy with this, and Jessie sends out Mimikyu, whose attack is deflected back at the balloon. Ash has Rowlet use Leafage which pops the balloon. This sends Team Rocket falling towards the ocean, only for Bewear to run across the water and catch them before running off. After Lana checks on the Pokémon, Ash compliments Popplio's work. Popplio creates a big balloon at Ash's request, which floats him and Pikachu into the air, only for it to pop sending them falling down.