Ecco the Dolphin gen (USA, Europe, Korea)

Air Meter Stays The Same (Official Codes) by Mr. Book

FFB636:0003

Almost infinite breath/Note by Galoob

AKRT-JA64

Charging a school of fish restores health completely instead of partially by Galoob

HCBT-LAEW

Ecco accelerates faster when using just the directional pad. by Tony Hedstrom

G29A-JA7C

Ecco has a much higher top speed when using just the directional pad./Note by Tony Hedstrom

931A-JAE2

Ecco swims much faster when using the C button. by Tony Hedstrom

AC9T-K2JY

Ghost Ecco (Use The D-Pad And C To Move/Swim) by Hacc

FFB63E:0011

Health Meter Stays The Same (Official Codes) by Mr. Book

FFB635:0038

Infinite Air by Parasyte

FFB636:0400

Infinite Health by Parasyte

FFB634:0040

Invincibility (infinite air, infinite energy). by Tony Hedstrom

RHZT-J6V6

Invincibility (Stars) by Hacc

FFB7CC:000A

Level Select by blindpainkiller

FFA61C:00??

Most Jellyfish And Some Other Enemies Restore Bealth Instead Of Taking It Away by Galoob

SW2A-KGPJ
HC2A-JAFL

Most jellyfish and some other enemies restore breath instead of damaging health by Galoob

SW2A-KGPJ
TC2A-JGFL
E42A-JAFN

Octopus is fatal by Galoob

HAVT-NAFC

Pause the game and press Right for Debug Menu/Note by terpsfan101

AR6T-KAX4
RG6T-J6YR

Protection from most jellyfish and many other enemies by Galoob

AL2A-JA7L

Protection from octopus by Galoob

AAVT-NAFC

Protection from spiked shells and some other enemies by Galoob

ALZA-JA5Y

Swim through rocks./Note by Tony Hedstrom

RGJT-J61N

Swim Through Walls by Helder

ACXT-JA60