Bubbly Basin is in a bit of a ruined state when you first arrive there in Pokopia. You’re given lots of different tasks to restore it to its former glory, though, including constructing a massive, beautiful building. One of the key items you need for this task is Ocean Doors.
The huge building Popplio tasks you with building will eventually be revealed as an ocean temple, which is why you need to assemble lots of intricate construction pieces for it. The vast majority of the assets you need are fairly easy to acquire, but the Ocean Doors can be a bit tougher to unlock. If this part of the process has you stumped, here’s where to find Ocean Doors in Pokopia.