i think it was the zoras..the big fish that gives you the last pearl(i cant remember his name) looks kind of like lord jabu-jabu and the zoras r greatfish hence the name greatfish isle
There's no Zoras in WW, they all evolved into the rito
Yes, the Zora did evolve into Rito, as depicted by Medli being Laruto's descendant. If you look closely around the island, you'll see what looks like the ruins of a village. My theory is that Hylians inhabited the island, and that maybe that is the race that Jabun protects, much like Valoo does the Rito and the Deku Tree does the Koroks.