Humanity didn't flee to the ocean. It was built for it.
Two generations of bio-engineering and surgical evolution later, The Shallows is their city: high-tech, humming, imperfect. Not a last resort. A civilization in progress.
Calistya is a groundwalker - half-adapted, half-committed, priced out of the Full-Gill Enhancement that would make her whole. No gear, no limits, no more being told she swims like she doesn't belong. Just the open ocean, endless and free.
She can't afford it. She's an orphan. That's just life.
Until the day she dives too close to The Deep.
Below the city's light, at the edge of the abyss where sentinels don't go, she sees a boy. No oxygen rig. No surgical scars. No implants. Just skin, and something about him that shouldn't be possible.
He shouldn't exist.
He looks at her once. Then he's gone.
When her best friend Khrystal vanishes into the abyss chasing the same impossible truth, Calistya faces a choice: stay safe inside a city that was never quite home - or dive deeper than her gear was ever designed to reach.
Down in the dark, she'll discover that evolution didn't wait for surgery.
And whatever came first is still down there. Watching.