Where to go after got the Nature form? (spoilers)

[Turniper]

Hello! I think someone has already asked something like this, but it is hard to find something without reading too many spoilers...

So far I have brought several ancient beings to peace and heave three forms, Energy, Beast and Nature. Apon beating the third boss, the one in the Kelp forest, and getting the Nature form, I do not know where to go. Of course, I have just missed some passage, but I cannot find any way.

Also I have found a Fish Cave, wich obiously contains some secret, but cannot figure it out.

I would deeply appreciate some hints. Thank you!

[Alphasoldier]

Singing, the secret is singing.

[Xocrates]

Try to explore other areas you haven't gone yet.

I heard the fish cave has great acoustic.

Or, being blunt: [Spoiler]Go back to Open Waters and then head east until you find Mithala. In the fish cavern lead the fishes of each color to the stones with the associated symbol[/Spoiler]

[Turniper]

Thank you, I shall try what you said!