Transiting the South Shore of LI I generally just follow a 40 ft. depth contour. The bottom is very regular and even. I think the puts me about a half to one mile off the beach, but I have never measured it.
If you are from Cape May, you are probably familiar with running inlets. But only the Shinnecock Bay inlet is "improved" like Cape May inlet. And do some trip planning. Unless you have an unusually fast sail boat, you cannot make the run in one day. So you either go overnight or come into an inlet for the night.