In South Australia, once caught, tunas are harvested in tuna pens where they are stuffed to reach a minimum weight before they can be sold. One tuna pen can be worth several millions dollars. The presence of a shark in the pen, hunting for tuna, can cause damages worth thousands of dollars. To avoid any loss, a crew member is required to free dive in the pen to wrestle the shark out of it. The most dangerous job in the world?