While on a boat, hold X and repeatedly tap Circle. You should now be able to play fifteen puzzle mini-games.
Completion bonuses
Successfully complete the game to unlock the Art Gallery (allows you to view game art you have unlocked), Bestiary (displays information on monsters you have defeated), and Music Player (allows you to play any BGM from the game) under the "Extra" option at the main menu. Successfully complete the Labyrinth Of Time to unlock the Time Chamber, which allows you to revisit any floors of Labyrinth Of Time you have already completed.