EASTPORT, Maine — When undersea diver Scott MacNichol of Perry first saw the large shape circling him in Broad Cove on Saturday afternoon, he knew exactly what it was: a shark, a big shark.

MacNichol, 30, was about 28 feet down in the cove, also known locally as Burnt Cove, filming the ocean bottom and taking samples from an empty salmon pen. He estimated the shark was 8 feet long and 300 pounds.

“That shark wasn’t there for the salmon. There were no fish, no food,” he said.

But the shark was clearly interested in MacNichol and proved incredibly aggressive, he said.

“It circled me two times and then began jabbing at my camera,” MacNichol said.