No more metaphorically talking about “the heart” until you bother to define what it means.
Rare Earth elements (elements 57-71 plus 21 and 39) have been found to repel sharks. The reason appears to be that they create an electrical current with the shark’s skin, effectively given the marvels of evolution a shock when they get too close. One study found that when the metals were used in certain types of commercial deep sea fishing, incidental (and unwanted) shark captures dropped by about 1/3.
(Also, these elements are called “rare Earth” not because they are rare but rather because they are notoriously difficult to tease away from other substances.)