In 2003, teenager Bethany Hamilton lives in Kauai, Hawaii with her parents Tom and Cheri, and two brothers, Noah and Timmy. All are surfers, but she and her best friend Alana Blanchard have grown up with a passion for the sport and enter a competition. Her church youth ministry leader, Sarah Hill, is disappointed when she has to withdraw from a planned mission trip to Mexico because of the contest.
À l’issue de Sharknado 5: Global Swarming (2017), la tornade de requins avait dévasté la Terre et saccagé le patrimoine de l'humanité, de la Muraille de Chine aux Pyramides d'Égypte. Humanité dont il ne restait d’ailleurs plus grand monde. Fin Shepard (Ian Ziering), se retrouvait seul, errant dans un décor de fin du monde.
Luke (Damian Walshe-Howling) is delivering a yacht to a customer in Indonesia, and invites his friend Matt (Gyton Grantley) and Matt's girlfriend, Suzie (Adrienne Pickering) to join him as he sails there. Also joining them is Matt's sister (who is Luke's ex-girlfriend) Kate (Zoe Naylor) and fellow sailor Warren (Kieran Darcy-Smith). To get to Indonesia, they must sail through a coral reef. On the second day of their journey, the yacht strikes part of the reef and capsizes when the keel is destroyed.
London-based gangster George Thomason and his right-hand man, Ken Pile, an animal lover with a bad stutter, plan a jewel heist. They bring in two Americans to help: con artist Wanda Gershwitz and "weapons man" Otto West, a loud-mouthed Anglophobe who fancies himself an intellectual and hates being (correctly) called stupid. Wanda and Otto are lovers, but they hide this from George and Ken, pretending to be brother and sister, so Wanda can work her charms on them. The robbery goes well, and the thieves get away with a large sum in diamonds. However, they are briefly spotted during their getaway by Mrs. Coady, an elderly lady walking her three dogs. The group then hide the loot in a safe in an old workshop. Soon after, Wanda and Otto betray George to the police and he is arrested. They return to collect the loot, with Wanda planning to double-cross Otto as well, only to find that George has moved it. Wanda decides to seduce George's barrister, Archie Leach, so that he can persuade George to plead guilty and give up the location of the diamonds. Unhappily married, Leach is brow-beaten by his vindictive wife, Wendy, and spoiled daughter, Portia, and he quickly comes under the spell of Wanda's charms.