At the Options screen, highlight Back before starting gameplay and press Up, Up, Down, Up, Down, Down, Start.
Fishing boat
Unlock all bonus tracks. Then at the boat selection screen, highlight the "Thresher" boat, hold L + R and press the View button twice. Finally, select the "Thresher" boat to drive a fishing boat.
All Tracks in Two-Player Mode
Play each race in two player mode and win to unlock secret tracks (for two player only). Eventually, you'll unlock all the tracks and then all the secret boats.
Race as the Tiny Titanic
You have to beat the easy courses in the top three to get the medium courses. After you have the medium courses then beat them by placing in the top two to get the hard courses.Beat these by placing first in all the races to get the bonus tracks. Beat the first three bonus tracks in first and you will be able to race with the most awesome boat in the game. The Tiny Titanic.
Arctic shortcut
On the Arctic Circle level, look for a shortcut on the left that takes you over an iceberg with penguins on it and through the hull of a big ocean liner.
Quick turns
On tight turns only, hit the brakes to bring the nose of your boat around more quickly.
Shortcuts in almost every track
Lost Island - Shortcut through the 1st waterfall right before the 1st Checkpoint.
Lost Island - After racing through the huts with spears flying out of the huts, veer to the left and you will see a rock. Race towards there and there will be a shortcut through the mountain.
Arctic Circle - Right before the 1st checkpoint, race up the ramp right between the 2 houses.
Arctic Circle - After exiting 1st tunnel, between the 2 arrows. Hydro jump into the hole through the mountain.
Arctic Circle - Enter the ship on the left side of the track, near the end of the race. Its right where the penguins are hanging out.
Greek Isles - First waterfall located on the left side of the track.
Lake Powell - 1st Waterfall - Shortcut.
Lake Powell - Near the end of the track, there will be 2 docks located on both the left and right side. There will be a ramp between those 2 areas, hydro jump on the left side of the dock.
There will be an opening to the mountain with a hidden booster.
Basically the shortcuts are mostly behind waterfalls.
Lost Island - Jump through the flaming volcano, to get an extra 9 second booster.
All Tracks
Complete one of the easy tracks in a good enough time for a high score. Then at the screen were you enter your initials enter ?PB. This should unlock all the tracks and boats. If that does not work then try ?DL.
