The town scenes were filmed in Edgartown, MA.(east side of Martha’s Vineyard) This is where you see all the white houses and picket fences.
Most of the water shark scenes were filmed on the west end of Martha’s Vineyard in and around the town of Menemsha, MA.
When they take the water ferry boat across the harbor, I believe they were going over to Chappaquiddick Island. Made famous by the swimmer Ted.
The lighthouse is at Gay Head. When the boat heads out it is the Menemsha harbor. Yep, the ferry is the Chappy ferry. Not sure which Beach they used. it could be the one between Edgartown and Oak Bluffs s there is a "pond" there under the bridge.