She'd loved a human once, a long time ago, when the seas were fiercer, the humans were weaker, and the world was younger.
She'd loved a human once, when her father ruled the waters, when her sisters sang the oceans to sleep, when sea witches lurked in the shadows.
She'd loved a human once, and died of it, when her name had been Ariel and she hadn't been a goddess.
But she was stillalwaysforever a child of the sea, and the sea took back what belonged to it.
She'd loved a human once, and turned into sea foam, absorbed into waters which are cold, distant, and uncaring, and she remembers only enough to grieve the loss of something precious (she doesn't remember his face, his voice, his smile, or the way he made her heart beat faster – the tides are her heartbeat now, and they beat with the unchanging, continual cycles of the moon).
She thinks, if she could remember, that this pirate, Davy Jones, would remind her a bit of him, the boy she'd loved, when she was young and full of emotion. But all she knows is the way he stands on his ship and stares out into the ocean, with a face full of longing and a heart of a sailor. She doesn't have a heart to beat faster, but if she did it would beat for him (for the memory of a boy he reminds her of). She gives him what she can, and if it's not fair to him, well, humans have been falling in love with the sea for centuries (if the sea ever falls in love with humans, only the tides know).
The sea is good at taking – fishermen, sailors, pirates, ships, hearts, souls, but it's never been good as good at giving back. It grasps what is offered (and what is not offered) and clings to it, buries it deep in its depths, so no one can find it and steal it away (she chose the name of her rebirth, Calypso – I will conceal – for precisely this reason).
This story can only end in tragedy, but it's a tragedy that will leave Calypso untouched (Ariel would have cried and screamed and sang her frustration, but Ariel loved a human once and now Calypso is all that's left).