No, bettas and sharks cannot live together. Bettas are freshwater fish, while sharks require saltwater to survive. Furthermore, the difference in temperatures between a betta's optimal temperature of 78-82 degrees Fahrenheit and a shark's optimal temperature of 75-80 degrees Fahrenheit would make it difficult for them to coexist in the same tank. Additionally, bettas are smaller than most species of shark and could easily become prey if kept with them. Ultimately, keeping these two species together is not recommended due to their vastly different needs.