Ecco the Dolphin: Defender of the Future

At the title screen, hold L1 + L2 + R1 + R2 and press X(2), Circle(2), X, Circle, Up, Down(2).

Successfully complete the game on the hard difficulty setting. The Up & Down level will shimmer, and you can now access both 2D bonus levels:

Passage From Genesis level
As you start the Up & Down level, swim around the cavern until you find the Info Crystal. Below it is a hole that leads downward. The current is too strong -- you cannot swim down it. Look for the boulder just right outside the alcove where the hole is located. Push it into the hole and stay directly behind it. You will enter a room with four stone pegs. Above those pegs is the power of Sonar. Get the Sonar and use it in the small opening of the pegs. A little light should appear. Quickly light up all four and a door below will open to the 2D level.

Pathways From Nowhere level
After you make your way up the geyser, you will find a big ring with a spot of light in the middle. In that same area are many power jewels. Find them and bring them to the ring. Two are above the water, one is under the stone shack-like thing, and the rest are around the other side of the pool. After you have collected all of them. it will open the way to the bonus area.

On the Powers of Levitation level, swim to the large central building underwater, and circle it until you find the Information Shard. Enter the structure here, and head down the tunnel until you find an oval door near the bottom. This passage is divided by doors that dilate open when you get near them. Head straight down the tunnel until you reach the room at the end. There you will find a clan member and a bubbler in the center of the chamber. Turn and face the entrance, and you will notice an oval section of wall to the left moving slightly in the current. Swim through it to find a secret room. Inside is a stealth power-up. Take it and return straight back. There is a pair of yellow lights at the back of the room. Touch your nose to the right one to be taken to Dolphin's World Championship soccer match.

Go to the Powers of Levitation level and find your way to the room where the clan General is located. Swim through the side of the rubbery wall. On the floor near one of the orange lights is a football. Get it, then go to the level selection screen. An option for the Dolphin Soccer mini-game will appear at the bottom.

Do the following (you will need a memory card).

Go to the [PLAYER MENU] screen and choose [NEW GAME].

Enter [GYU GYU ???] where ??? can be any three letters you want.

Press the [CIRCLE] button on the controller. If the cheat has worked then a plant on the left side of the screen will release a huge stream of bubbles.

Press the [X] button to create the save file, then return to the main menu.

If you go to the [LEVEL SELECT] screen you will find that ALL of the levels have been unlocked. You may now select any level you want.