The Ocean

While it could be easy to write this off as Zeus, Poseidon or even Triton manipulating the waves to do the council's bidding, this is not actually the case. "The Ocean" is in fact a nature spirit, brother to the great spirit Te Fiti. And when his sister was corrupted when Maui stole her heart, he wanted nothing more than to restore her heart and bring life back to his world. But despite his best intentions, he couldn't directly put the heart back or risk killing her on accident. So, The Ocean kept asking the council for a way to help save his sister.

The council did all they could without becoming overbearing, but as the world began to die, they had to present the Ocean with an Ultimatum: come up with a plan, or we'll have to force our way onto this world to save it. The Ocean proposed a slower but still effective solution: raise up a champion among a Polynesian to save them. The council agreed, sending a member to keep watch once the ocean chose its champion.
And so, the ocean chose Moana as its champion, gave her the heart of Te Fiti (it could easily have picked it up after all), and helped inspire her to go be the hero it wanted. And of course, fling her back onto her boat when necessary.
- Moana didn't always stay strong though, and however reluctantly at what would come next, the ocean would have respected her decision to give up. Only the consequences would have been a sea invasion by Triton's forces to defeat Te Ka. Thankfully, she eventually chose to never give up, and with her love and care, the ocean got people sailing and seeking life over itself again.
  - Oh and Another fun fact: The Ocean, while mostly uncaring in general, does have a soft spot for children. Hence why he chose to rescue Maui at a young age and pass him on to live a better life as a demi-god.