In a near future where a series of environmental disasters has left much of the country underwater, Pearl lives on a floating oyster farm with her father and younger sister, Clover. Following her mum's death several years earlier, Pearl refuses to set foot on land, believing her illness was caused by the poisons in the ground. Meanwhile, Clover dreams of school, friends and a normal life. Then Nat comes to spend the summer at the sea farm while his scientist mum conducts some experiments. Leaving behind the mainland, with its strict rules and regulations, he brings with him a secret. But when the sisters promise to keep his secret safe, little do they realize that they may be risking everything.