At breakfast aboard the Stellosphere, Miles asks Stella for two bowls of Orbit O's with Marsberries for him and M.E.R.C. Unfortunately, he is told that she is out of Marsberries. So, Miles decides to pick some from the garden, but when they get there they noticed that everything in it is looking brown. Loretta tells him the garden is drying up and they are unable to water anything because Leo had to use the sprinkler parts for a new invention as it's for an emergency mission. Miles wonders what his dad is building and decides they should go see if he has finished with it.
Leo is in his workshop working on his invention when Miles, Loretta and M.E.R.C. come in. Leo apologises to Loretta for using the sprinkler parts for his invention and promises her that the replacement parts would be soon. He then introduces the kids to his latest invention called the Water Maker. Miles asks if it actually makes water and Leo confirms this with a demonstration. Leo puts two cups over the machine's faucet, it pours out the water and gives them to Miles and Loretta to drink. Then just as Miles is about to ask what the emergency mission, Stella informs them that they have an incoming call from the Tomorrowland Transit Authority. Leo, Miles, Loretta, and M.E.R.C. arrive on the bridge and meet up with Phoebe, who is commenting on Admiral Crick newly grown a beard. To him it tickles but brings out his smile, to which Admiral Watson agrees on. He explains to the Callistos that Crick wanted to see what it would be like to stop using water, and since then has stopped shaving. Upon asking Loretta Crick, this brings up the subject of their mission; planet Sandrosk is having a severe drought because planet is out of water for the Mendelsons to drink. According to Leo, the planet's water reservoir is empty as it has not been raining for a very long time, which is why he had been building a Water Maker. The Callistos mission is to take the Water Maker to Sandrosk as quickly as possible. With assurance that they will have water flowing on the planet, the Callistos accept the mission and set a course for planet Sandrosk.
Sad that there is not a water maker for the garden, Miles gets the idea to use the Water Maker that Leo made until they get to Sandrosk. Miles and M.E.R.C. bring the Water Maker to the garden. Miles decides to use it on the tomatoes first. He pulls the lever and turns the dial on the machine which starts pouring out water, but not much is coming out. So, Miles turns the dial to full blast, which causes the Water Maker to start shaking. Suddenly, one of the machine's hoses break off spraying water everywhere and causes the machine fly like a jet pack. The lever to stop it also breaks off. Realising his mistake, Miles wonders how he is going to shut it down as the Water Maker flies away. Meanwhile on the bridge, Leo and Phoebe notice the ship is flowing with water. Loretta, who surfed on her blastboard to get to bridge, tells them the Stellosphere is flooding. Miles then arrives on the bridge and admits the flooding was his fault. He tells his parents that he tried to use the Water Maker on Loretta's plants but broke it. Leo asks where the Water Maker is currently, and Miles tells him it blasted out of the garden and has no clue where it went. Phoebe asks Stella if she can locate the Water Maker, but due to it moving so quickly she is unable to track it. Seeing how fast the machine is flying on the screen, Leo tells Stella to seal the doors to the engine room because if the power cells get wet they would be ruined. She seals all doors to the engine room, but reports that water is still pouring in through a vent. As the mission has now become an underwater one on the Stellosphere, the Callistos must swim to find the Water Maker and turn it off.
The Calistos activate their aqua mode space suits and begin swimming in the ship. While Miles and M.E.R.C. swim through the kitchen, Loretta swims through one of the hallways and finds the Water Maker flying past her and into the garden. Stella informs the family that there is one minute and seventeen seconds until the water reaches the power cells. Miles and M.E.R.C. find the machine flying out of the activity room and takes the multivator to the hangar. Loretta, Leo, Phoebe are already there looking for the Water Maker when it blasts out of the multivator. Miles who then chases the machine, gets on it and is taken for a wild ride. Leo tells him to open the control panel and flip the switch inside. Miles opens it and flips the switch, which shuts the machine down. Stella informs the Callistos that the water has stopped flowing into the engine room. Leo notices the machine got banged up, saying it will take a while to fix it. Phoebe decides they should call the admirals and let them know they will be delayed in getting water to Sandrosk. However, knowing the Stellosphere is full of water, Miles suggests they can transport it to Sandrosk. Leo says it will give them enough water until he can get the Water Maker working again.
The family heads to the bridge and blasts off to Sandrosk. Mesa, one of the planets inhabitants, contacts the Callistos. Noticing the Stellosphere full of water, asks the family if everything is all right. Phoebe explains they had a small change of plans with Miles adding that they got a head-start on the water-making. Loretta tells him to get ready as they are about to "make a splash". The ship approaches the planet's surface, and with everyone holding on and on Phoebe's orders Stella releases the water that fills the water reservoir. With the Water Maker all fixed up and connected to the water reservoir, Leo gives Mesa the honor of activating it. Mesa thanks the Callistos for their help, and the family returns to a wet and messy Stellosphere.
Miles apologies for using the Water Maker without asking and not really knowing how. Miles is forgiven as long as he promises to ask first if he does not know how to do something. Looking on the bright side, Phoebe admits that turning the ship into a temporary water-tanker did help get water to Sandrosk faster and bring the bio-garden to life. To get the ship dried out faster, Leo reveals he had been working on another invention that will fan-dry the interior of the ship. Phoebe says they will start printing them on the Solidizer immediately. M.E.R.C who press the green button on the multivator get splashed by the extra water from the flood, causing the family to wet again.
- Justin Felbinger as Miles Callisto
- Fiona Bishop as Loretta Callisto
- Tom Kenny as Leo Callisto/Mesa Mendelson
- Olivia Munn as Phoebe Callisto
- Dee Bradley Baker as M.E.R.C.
- Grey DeLisle as Stella
- Danny Jacob as Admiral Watson
- Diedrich Bader as Admiral Crick
- Miles likes having Marsberries in his Orbit O's cereal.