Stone Pillar Seal

Walkthrough: Mario and Cappy will arrive in Seaside Kingdom at the town of Bubblaine. As you arrive, you will discover another giant monster is terrorizing the kingdom, this one stealing the town's supply of Sparkle Water via the carbonated tower. Of course, it will be up to you to stop it. Begin by going around the Odyssey Airship, the same that has a ledge behind that you can wall jump up in order to find some Purple Coins. After you do, follow the Bowser tracks toward the first of four different fountains that have been plugged by the antagonist himself. You must open these fountains by using nearby buttons hidden under given seals around the town.

The first seal is the Stone Pillar Seal. Right at the edge of the water past the first plugged fountain, you should be able to see creatures known as Gushens running around a platform with the first button. Quickly capture one of the nearby Gushens with the help of Cappy, and then use it to reach said platform. Doing so will earn your first Power Moon, the same that will also shatter the seal covering the first button that can unlock one of the four fountains. This will upset the giant monster.