Lure And Lash. Undertow Sins, #17

The ocean doesn't forgive. Neither does he. Zephyrine Kade is looking for a dead man's grave and a living man's ruin. Armed with her late father's encrypted journal, she books a charter on the Harrow under a fake name, determined to expose the truth behind her father's disappearance at sea eight years ago. The target of her revenge? Barrett Crowe, the quiet, dangerously observant son of the man who killed him.
But Barrett knows exactly who she is from the moment she steps on the dock. When a violent tropical storm hits the Florida Keys, Barrett disables the boat's radio and anchors them in a remote mangrove channel. Trapped in a claustrophobic, sweltering cabin with a morally grey captain who controls the water, the food, and her only way back to shore, Zephyrine realizes the hunt has turned into a hostage situation.
As the storm rages outside, the psychological tension between them reaches a breaking point. The boundaries between bitter hatred and a magnetic, undeniable attraction blur in the dark. But the greatest shock comes when the water clears. Zephyrine discovers that Barrett hasn't been hiding from his father's guilt-he's been trying to drown it. For three solitary years, he has secretly dived into the black waters to protect her father's legacy, becoming the sole guardian of an extraordinary underwater secret.
To save her father's life's work, Zephyrine will have to trust the son of his killer. But in deep water, trust is just another anchor that can drag you under.