Long Island has many great sites for shore diving. Listed here are just a few for which I have scavenged descriptions. For a complete listing, pick up a copy of Dan Berg's Long Island Shore Diver at your local dive shop.
Do not ask for numbers - I will not give them out !
Looking roughly south: Sandy Hook is barely visible at upper-right, Rockaway inlet at the upper-left, Brooklyn at lower-left, Staten Island at lower-right. The shipping channel is also plainly obvious.
There are two actual Ponquoque bridges, the new one and the old one. You crossed the new bridge to get to the former Foster Road. The old bridge is where you will probably dive, although nothing is stopping you from diving the new bridge. Don't get caught in the channel between the two bridges, however, because it is considered a channel and it is illegal to dive in a channel in the town of Southampton. With that in mind, there is usually good parking at the bridge, but you will have to do some walking in order to get into the water.
Now, most people would look at the heading on the page and think that I was crazy for diving near a nuclear power plant. Just to calm your fears, this power plant was never brought online, so there is no chance of getting radiated at this location (barring a nuclear war while you're diving). With that said, Shoreham can be a very interesting dive. Located on the north shore of Long Island (I don't know the name of the town, look on a map), it is a shallow dive with an average depth of around 16 ft. Visibility tends to be anywhere from 3 to 10 ft.