Quarry And Quarrel. Undertow Sins, #49

The water remembers who it belongs to. So does he. For six years, hydrologist Delphine Voss has broken the law to swim in the deep, emerald waters of an isolated limestone quarry. It used to belong to her father, before it was stolen by a rival family and drove him to ruin. She thinks her secret is safe. She is wrong. Silas Thatcher, the scarred and rigidly controlled current owner, has watched her every single time.
He has memorized her strokes, left her towels, and silently bolted safety anchors into the rocks she climbs. He never stopped her. He never spoke to her. Until now. When a historic, 115-degree heatwave literally melts the only asphalt road out of the property, Delphine's car is rendered useless. Trapped off-grid with cell towers burning out and the water level dangerously dropping, she is forced into a tense survival pact with Silas.
He controls the water, the rules, and the locks. His restraint is absolute, but it is its own form of cage. What Silas doesn't know is that Delphine is hiding a secret of her own-a government assessment that could strip him of the land forever. Locked in a suffocating psychological standoff, the boundary between protector and captor blurs. As the heat pushes them to the breaking point, Delphine must decide if the man who has spent years silently watching her is her greatest threat, or the only solid ground she has left.