A category 4 hurricane inundates the entire towns of: Amityville, Lindenhurst, Babylon, West Islip, East Islip, Bayshore, Gilgo Beach, Cedar Beach, Great South Beach, Fair Harbor, Cherry Grove, Cupsogue, Westhampton Beach, Watermill Beach, Wainscott Beach, Plum Island, Gardiner's Island, Orient, Shelter Island (except for a few high points), Greenport, North Haven, Amagansett Beach, Napeague Beach, Montauk, Woodmere, Valley Stream, Linbrook, Long Beach, Atlantic Beach, Freeport, Merrick, Wantagh, Lido Beach, Jones Beach, and Tobay Beach.
This is exactly what created "The Inlet", south of Dewey Beach DE. And if I remember correctly, The Inlet was created by a mere Nor'easter, not a strong hurricane.
Think what Isabel could do. Hope the map-makers are ready for some extra work. :)