At beging of the level there should be 2 rocks. Face up toward them and press B (they will break). Swim through and you will be in the first level.

Turn so that ecco is looking at you. While he is looking at press start and quickly press A, B, C, B, C, A, C, A, C, A, B.

Turn Ecco left or right and pause the game while Ecco is facing towards the screen. Press (A), (B), RIGHT, (A), (C), (A), DOWN, (A), (B), RIGHT, (A), and then unpause. You will now never die from lack of air or injuries.