Wakeboarding Unleashed Level select
At the main menu, press X(4), B(4), Y(4), X, B, Y. If you entered the code correctly, a message will appear.
All boarders
At the main menu, rotate the Right Analog-stick clockwise fifteen times. If you entered the code correctly, a message will appear.
Second and third boards
At the main menu, press Up(2), Left(2), Right(2), Down(2), Up, Left, Right, Down, Up, Left, Right, Down. If you entered the code correctly, a message will appear. Alternately, complete the Florida and Delta Stage challenges to unlock the second and third wakeboards.
Completion bonuses
Successfully complete all levels to unlock the credits stage, a video of your character, and Summer, the first hidden character.
Play as Jordan
Make a perfect run during all the Star Search challenges (collect every possible star) to unlock Jordan, the second hidden character.
FMV sequences
Successfully complete the game to unlock the FMV sequence for that character.
The image featured at the top of this post is ©Square Enix.