Ecco The Dolphin Wiki
Ecco prologue by seeraphine

For five hundred years, dolphins and humans had lived together in unity,
harmony, and fellowship.  Together, they set out to explore the great unknown.
Peace and friendship were offered to all who would welcome it.  But there were
forces for whom aggression was the highest calling.  Creatures known only as
'The Foe' regarded the Earth with envious eyes, for humans and dolphins were
their hated enemy.  From time beyond memory the Foe had gone undefeated.  They
devoured, dominated and annihilated all in their path.

But humans and dolphins brought their age of conquest to an end.  Driven to the
brink of defeat, The Foe plotted vengeance on Earth.  But the few caretaker
dolphins who remained behind were not defenseless.  Protected by their greatest
creation, the Guardian shielded them with its immense power.  Undeterred, the
Foe persisted seeking a moment of weakness. [And] In this time of crisis lived a
young dolphin named Ecco.  He was destined to become the only hope for humans
and dolphins... [Ecco] Defender of Earth's future.