Authorities are monitoring the waters off the North Carolina coast after a string of shark attacks that began in June. There have been at least seven attacks by sharks reported. There are six types of sharks that could be responsible for the attacks -- blacknose shark, sharpnose shark, bull shark, tiger shark, blacktip shark and spinner shark. However the challenge is that sharks who attack and swim off are difficult to identify, according to Dr. Louis Daniel, director of the North Carolina Division of Marine Fisheries. Read more about the six sharks' unique characteristics.