Rare-earth magnets repel sharks

... the magnets overload a shark's ampullae of Lorenzini, small vesicles and pores around the head that form part of a subcutaneous sensory network ...

However,

Hermann cautions that the magnets appear to have an effective range of only 10 inches. Also, you'd need to align the magnetic poles outward and keep the magnets from clicking together, and once you had the necessary 10 to 20 pounds of magnets all over your body, you'd sink. So, at a cost of about $5 a magnet, you could theoretically turn yourself into a $400 shark-safe anchor at the bottom of the sea.

Also, some pheromone-based sunblock/repellent lotion.