No, sharks are not a concern. We understand the fear, but it is highly improbable to see a shark, let alone be attacked by one. Statistically speaking, you are more likely to be struck by lightning twice or hit on the head by a coconut than you are to be attacked by a shark. The area we take our students surfing is over reef where an adult human can stand with their head and shoulders above water. These shallow waters are not where sharks tend to be found or even like to swim as they like to stay further out in deeper waters.  Sharks will also not attack a human on purpose as we are not a food source that they are interested in which is why it is very rare to be attacked.
Check out One Ocean Diving: https: https://oneoceandiving.com. They offer tours on island to swim with sharks in open waters. Part of their mission is to try to help change people's opinions on sharks.  Their website may provide some new and interesting information about sharks, check them out.