Ecco the Dolphin Hints & Cheats

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.

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.

Enter the code SHARKFIN for infinite air and sonar.

AJPPOWAX is the password for this level

The Undercaves: UYNAINCC
The Undercaves 2: DQDIACCI
The Vents: FKWLACCA

The Lagoon: NDRBRIKR
Ridge Water: HYAUGFLV
Open Ocean: FNCQWBMT

The Ice Zone: DWFFZBMV
Hard Water Zone: QGDJRQLA
Cold Water Zone: MCLFRQLW

The Island Zone: UWXIOQLK
Deep Water Zone: EILQOQLC
The Marble Sea: XAKUQQLS

The Library: FDGXQQLC
Deep City: ZUVPQQLU
City of Forever: AABBRQLU

Jurassic Beach: PLABUNLT
Pteranodon Pond: FQREUNLI
Origin Beach: QXKIUNLX

Trilobite Circle: OBEMUNLX
Dark Water: JNXPUNLA
Deep Water 2: WSGAKNLC

City of Forever 2: ZBPIGPLD
The Tube: KUVEKMLK
The Machine: SDDBKMLG

The Last Fight: KNLMLMLC

NVNAINCR

When you are in the "password entry" screen, you can enter these "please" codes to reach the corresponding levels.

By entering an even combination of A's and N's in different sequences for your password, you can gain access to a variety of levels within the game. Here's a list of password combinations and the levels they take you to:

AANNNNAA: Deep City
NNNAANAA: The Marble Sea
AAAANNNN: Origin Beach
NNNNAAAA: Island Zone
NNNAAAAN: Undercaves
AAAAAAAA: Undercaves
NNNNNNNN: Welcome to The Machine
AAANNNNA: Welcome to The Machine
ANANAANN: The Vents
AANNAANN: The Vents
NNAANNAA: Dark Water
NANANNAA: Dark Water
ANNANNAA: Dark Water
ANANANAN: Hard Water
NANANANA: Hard Water
AANNANAN: Hard Water
NNAANANA: Hard Water

All other combinations will not work, and will transport Ecco back to the starting screen of the game.