The following are known Game Genie Codes for Ecco the Dolphin on SEGA Genesis.

• Almost Infinite Breath (Switch Off To Die If You Get Stuck)
  AKRT-JA64
• Protection From Most Jellyfish And Many Other Enemies
  AL2A-JA7L
• Protection From Spiked Shells And Some Other Enemies
  ALZA-JA5Y
• Protection From Octopus
  AAVT-NAFC
• Octopus Is Fatal
  HAVT-NAFC
• Charging A School Of Fish Restores Health Completely Instead Of Partially
  HCBT-LAEW
• Most Jellyfish And Some Other Enemies Restore Bealth Instead Of Taking It Away
  SW2A-KGPJ
  HC2A-JAFL
• Most Jellyfish And Some Other Enemies Restore Breath Instead Of Damaging Health
  SW2A-KGPJ
  TC2A-JGFL
  E42A-JAFN