A look at the chart shows the obvious jetty. It is on the north part of Long island Sound between Oyster Bay and Lloyd Harbor/Huntington

If you look just west of the entrance to the "hole" near the 6 foot depth markers, it shows the Rock Jetty. It also shows that you need to zig-zag to get in. I think it was a new moon, so at dead High tide I think the rocks were just under the water level.