A man finds himself cast away on an uninhabited island after being swept away by a storm. He awakens to discover his surroundings, which include abundant fresh water, ripe fruits, and a lush bamboo forest, all overshadowed by a distinct rock hill. As he spends his nights there, he begins to experience hallucinations, imagining a bridge leading to freedom and even a quartet serenading him on the shore. Driven by desperation, he constructs a raft from the bamboo, attempting to sail to safety. Unfortunately, each of his attempts is thwarted by an elusive creature lurking beneath the waves, culminating in a startling revelation: the creature is a giant red hawksbill sea turtle.
One evening, filled with rage, the man strikes the turtle with a bamboo stick, flipping it onto its back and leaving it stranded. Yet, as he grapples with guilt while crafting a new raft, he goes to help the turtle, but finds it too heavy to turn over. When he fetches water for it, he returns only to discover that the turtle has perished. Heartbroken, he sleeps beside it, only to wake up to a shocking sight: a red-haired woman lying unconscious within the split shell. He cares for her, building a shelter to shield her from the sun, and when the rain arrives, she awakens and swims. Together, they cast off the turtle shell and their journey intertwines as love blossoms.
Their joy multiplies with the arrival of a red-haired son, who flourishes in his environment. One day, while exploring, he unearths a glass bottle, prompting his parents to share their adventures through vibrant pictographs. An outing leads the boy into the sea, where he discovers his gift for swimming alongside the green sea turtles. However, a tragic tsunami eventually ravages the island, scattering the family. In the aftermath, the young boy discovers his wounded mother while desperately searching for his father. Rapidly, three turtles accompany him as they find the man clinging to a bamboo tree, just in time to save him from slipping beneath the waves.
As years pass, a dream ignites within the young man, pulling him towards the vast sea. He envisions himself swimming atop a monstrous wave, gaining a broader perspective of the ocean's expanse. Seizing this moment of clarity, he bids farewell to his parents and swims away with the three green turtles. Meanwhile, the man and woman continue to inhabit the island, aging together in their secluded paradise. On a tranquil night, after a contemplative gaze at the Moon, the man closes his eyes for the final time. Heartbroken, the woman lays beside him, placing her hand on his as it transforms into a flipper; she reverts to the red turtle and makes her way down the shore, gracefully slipping into the ocean's embrace.
