Originating as a series of games during the 16-bit era on the Genesis, the Ecco franchise centered around the concept that underwater mammals are sentient. Most of the games do not feature humans at all, focusing on the native underwater life.
Ecco's exploits are usually centered around his travels through the seas and eventually through the time-space continuum. The first two games of the franchise - Ecco the Dolphin and Ecco: The Tides of Time- were intended to be the first two parts of a trilogy. However, the final game was canceled, and Ecco Jr. was released instead.
After taking a hiatus during the Saturn's lifespan, a new Ecco game was developed and released for the Dreamcast (and later, the Playstation 2) under the title 'Ecco the Dolphin: Defender of the Future'. This release disregards the events of the previous games, showcasing a society in which sentient dolphins and humans live together in harmony.
There has not been a new Ecco game developed since Defender of the Future, though the original game has recently seen re-releases on the Virtual Console, Xbox Live Arcade, and Steam.
As well as the video games that Ecco starred in, he also received a long-running comic series in Sonic the Comic, published by Fleetway.