In the game: sign in with Google, then open Menu → Delete my online data and tap it twice to confirm. Your online save, scores, friends, fleet membership, notification token and game sign-in account are deleted straight away.
By email: write to showfee.app@gmail.com from the Google account you play with, asking us to delete your data. We delete it within 30 days.
Guest captains keep no data between sessions. Wave battle and Story progress are stored only on your phone and are removed when you uninstall the game.