Captive of the Tide

The reclusive biologist Emma is sent to a remote‑island lighthouse for research, with supplies only arriving in a month. Following a shipwreck, she finds Kai, a gravely wounded genetically‑altered merman, on the shore. Savage at first, Kai attempts to kill her, yet forced co‑existence inside the lighthouse turns his killing rage into obsessive possessiveness. The Black Shark mercenary team lands to seize Kai, a bioweapon with immortal cells. They aim to harvest his life‑sustaining inner core alive. Emma repeatedly shelters Kai, who secretly kills lone mercenaries to defend her. Captain Vance traps Kai in an electrified cage using Emma as bait. Seeing human greed as the real evil, Emma chooses to stand with Kai. A fierce lighthouse battle breaks out. Emma uses chemicals to free Kai, and they fight side‑by‑side. Shot during their showdown, Emma falls into the sea, dying. Kai gives up his immortal core to revive her, losing most of his strength. After wiping out the attackers, Emma burns all experimental records. She leaves Kai temporarily to take down Black Shark. Five years on, the island lies abandoned. Emma lives quietly by the sea, and the weakened Kai stays with her. Escaping labs and hunters forever, they live peacefully amid the tides.