Nearly two decades after their life-changing summer, Hailey and Claire find themselves drawn back to the coastal town where they first met Aquamarine.

The mythical mermaid returns from the depths with an urgent plea for help, as her underwater kingdom faces a catastrophic threat that could destroy the balance between land and sea.

As the trio reunites, they must navigate the challenges of adulthood while rediscovering the magic and bravery of their youth.

The journey takes them deep into uncharted waters, uncovering ancient secrets and facing a dangerous new adversary who seeks to exploit the ocean’s power. Amidst the swirling tides of danger and mystery, the strength of their friendship is tested like never before.

They must work together to protect the blue heart of the ocean and ensure that the bond between their worlds remains unbroken. It is a story of courage, sisterhood, and the enduring power of a promise made across the waves.