The King and his men stole the Queen from her bed
And bound her in her bones
The seas be ours and by the powers
Where we will we'll roam
The first Brethren Court with the help of Davy Jones, trapped Calypso and bound her in human form as Tia Dalma. Since Calypso is the sea goddess, this tamed the seas, even seeming to give the pirates control over them.
Presumably, freeing Calypso from her human form returned that power to her. She summons a maelstrom that swallows Davy Jones and The Flying Dutchman.
But after that, do we ever see the effects of a freed Calypso?
This can be in the final acts of At World's End, or in the sequels, such as On Stranger Tides or Dead Men Tell No Tales / Salazar's Revenge.