High Quality Content by WIKIPEDIA articles! The BMT Sea Beach Line is a rapid transit line of the BMT division of the New York City Subway, connecting the BMT Fourth Avenue Line subway at 59th Street via a four-track wide open cut to Coney Island in Brooklyn. It has at times hosted the fastest express service between Manhattan and Coney Island since there are no express stations along the entire stretch, but now carries only local trains of the N service which serves the entire line at all times.