Ecco the Dolphin Cheats

Begin the game and move Ecco left and right. Press Start to pause the game while Ecco is turning. You have to pause it when Ecco is directly facing you. When you do that, press Right, B, C, B, C, Down, C, Up. If you did it right, a cheat menu that has options such as stage select, message test, sound test, and more, will appear.

Input a valid password, then press Start, and wait for the screen that shows the name of the level you're currently in with your password. Next, hold A and Start. Keep hold of A and Start until Ecco appears on the screen. Now press Start to unpause and you will be invincible.