3 links
DARK SEA : The Ultimate Ecco the Dolphin Resource
ecco-darksea.com
Ecco DARK SEA was founded to provide fans with all information and multimedia available in regard to these classic games, including their development.
Ecco the Dolphin - Wikipedia
en.wikipedia.org
Very thorough description of the complete Ecco the Dolphin series with a great introduction and information about each of the games.