TransWorld Surf Cheats

To take a trip under the water go to free session mode. Here you can
choose any person or board you want. Then go to Tavarua island. Go
around the island on the right side to where the buoys intersect with
the island. Go out  past the buoys and back in to draw the shark out.
Then go out a second time to have the shark get you. here the shark
should carry you under the island where you can swim around.        (no
waves go under here)

When you are in the water, hold White + Black. When your player surfaces, keep holding the buttons. Your character should go back underwater, except deeper this time, allowing you to stay under longer. If you come up to a wave, press L + White to go under it. Hold L + White until you surface. You will go underwater all the way to the bottom. This gives you a chance to stay under longer and look around.

To turn off all cheats during game play hit the Back button 4 times.

During gameplay, press Back, Up, Down, Left, Right, Left, Up.