Rare earth elements were not actually rare. They were hard to find. Despite that, they were common in magnets.
China was the biggest producer one of the most common rare earth elements: Neodymium. Neodymium was found in magnets which also contained iron. During the early 21st century, China started regulating the exportation of neodymium. This threatened the economies of the world. An American company called Molycorp opened its own neodymium mine in the United States. This took a bite out of China's near-monopoly. Meanwhile, scientists started making magnets that had less neodymium in them but still worked. Of course, neodymium and other rare earths would play an important role in fishing: Shark Repellant.
Tech Level: 10
A scientist named Patrick Rice discovered while repairing a tank that sharks were allergic to neodymium magnets. This got him interested and he wondered if sharks could be saved from fish hooks. There was one problem. Fish hooks were made of magnetic metals. Rice searched for a solution. It turned out that all rare earth elements were capable of repelling sharks by creating a small electric shark. The most common in use was samarium. It electrocuted sharks out of the way, but other fish were not put off by that. This saved sharks from fish hooks. Samarium was also incorporated into diving suits to keep sharks away when they not being studied. This was not the only application of samarium. When alloyed with cobalt, samarium made a supermagnet that could be used for medicine.