If your Sky Whale is wearing a snorkel, you can go underwater. The snorkel needs to be bought from the boosts menu.


Once you have purchased it, they will randomly appear throughout your game.

  

Once you see it, have your Sky Whale touch it so it can wear it and go underwater.
AR Mode:
Simply press the blue arrow button on the right side of the screen to go underwater and to go back over the water.