A remarkably detailed PDF of storm surge potential for all of Long Island is available at a Stony Brook University Web page maintained by Scott A. Mandia, a professor of physical sciences. A section of the PDF file is reproduced below.
A category 1 storm like Hurricane Sandy can be expected to inundate much of the Village of Sag Harbor, Sammy's Beach, the Gerard Drive peninsula, Louse Point, Springs around Accabonac Harbor, Amagansett near Devon and along Cranberry Hole Road, Lazy Point, Montauk Highway south of Napeague Harbor, Navy Road in Montauk, portions of downtown Montauk, and the Lake Montauk shoreline. Bay Point in Noyac would be cut off both from North Haven and from the west.
As was experienced during the 1938 Hurricane, Montauk would be cut off from the rest of the island by flooding on Route 27 (Montauk Highway) south of Napeague Harbor.