Complete each achievement to get the allotted gamerscore.

Unlockables

Big Blue Message (50) Find the glyph in Island Zone that tells you to find Big Blue.

Death Sonar (10) Acquire the Death Sonar.

Ecco the Hero (10) Rescue the dolphin family in The Lagoon level.

Game Win 2x (10) Complete the game 2 times.
Game Win 3 (20) Complete the game without dying more than 3 times.

Life Saver (10) Reach Ridge Water without dying.

Octopus Avoider (15) Pass the Undercaves without being hit by an Octopus.

Shark Killer (10) Kill 10 Sharks in a row.
Sonar Free (35) Reach the Dark Water Level without the Death Sonar.
Sonar User (10) Kill 30 enemies with the Death Sonar.
Songs in the Sea (15) Find the hidden glyph in Origin Beach ("Never have we heard...").

Undercaves Survival (5) Pass the Undercaves without dying once.

Enable the Super Cheat Menu - 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.

Final Level Password

The Last Fight: KNLMLMLC

Invincibility - 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.

Last Fight Password - AJPPOWAX is the password for this level

Level Passwords

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

Level Passwords 2

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

Level Passwords 3

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

Level Passwords 4

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

Level Passwords 5

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

Level Passwords 6

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

Level Passwords 7

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

Level Passwords 8

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

Undercaves Password

NVNAINCR

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

Password Effect
PLEASEHH City of Forever
PLEASEKK Deep City
PLEASEOO Final Fight
PLEASEEE Ice Zone
PLEASEFF Island Zone
PLEASEUU Marble Sea
PLEASEWW Open Ocean
PLEASEQQ Origin Beach
PLEASEGG Pteranadon Pond
PLEASEZZ Ridge Water
PLEASEII Undercaves