I suspect the shark was after the harbor seal briefly mentioned at the start of the article. But harbor seal got out of there, leaving the shark to look for targets of opportunity. Like a splashing human.
Apparently, way back, gray seals were abundant off Maine, as were the sharks that hunted them, but hunters drove the seals out of the area, so the sharks left. But in recent years, there has been efforts to bring back the gray seals.
There have been sharks teeth found in Penobscot Bay.
Wearing wet suits doesn’t help either....believed often mistaken fr seals.
I used to summer on an island in Penobscot Bay. Harbor seals were plentiful, hanging out on the tidal ledges. Never heard anyone mention sharks.