Get points
After you do a trick off a ramp press start and you will rack up awesome points!

Racing on a dolphin
At the Main Menu, choose Start Mode and choose a waterscooter and the Dolphin Park. While racing, take each ring and perform all stunts. If this went well, you will hear a dolphin sound. Now, on the normal difficulty level, choose Championship mode. Take the warm-up option. If you choose the waterscooter, then hold the joystick DOWN and press A until you start the race.

Get 3 Baby Dolfins
At The Title screen,Go To Championship,Pick the Level,Easy,Hard,Normal,Then Pick Warm Up And Do Everything The Dolpin does,If You Did It Right,The Dolpin Will Do A flip at the Dolpin Park Sign,Do This 3 Times And A Baby Dolpin Will Come After 3 Times,"If You Did What The Dolpin Did."When You Get It 9 Times And You Did What The Dolpin Did."Only 3 Baby Dolpins Can Come."

Ride a shark
Go to the practice mode and don't miss a single ring. When you are done get out to the main menu and do a 360 on the joystick 10 full times. If you are successful you will hear a load laugh.

Use a submarine
In the player selection screen press A, B, A, Z, B, R, L, A, A, B, Z, L, A, Start. This cheat will let you ride a small yellow sub (Twilight City is the best course to use it in).