The shark lunged at him and took a couple of bites at the camera before it swam away. MacNichol was shaken up but uninjured.
"He took a couple of bites at the camera. When he did that I was pretty much petrified," MacNichol said Wednesday. "If you watch the video, you can hear me screaming underwater."
He says the 300 pound porbeagle shark may have thought his camera was food.
Shark encounters are rare in New England. The last fatal shark attack in New England was in 1936, when a boy died after being attacked in Massachusetts, according to the International Shark Attack File at the University of Florida's Museum of Natural History, which tracks shark attacks.
The Associated Press contributed to this report.