There are many more of these communities in Suffolk County than in Nassau and as, previously stated, they are either luxury or 55+. They also tend to sell out very quickly and you'll probably need to wait for a resale. If Plainview is of interest to you, there is one currently available.
Yes, there are several gated communities with indoor + outdoor swimming pools as amenities. They are located in North Hills + in Port Washington. These communities are either luxury and/or 55+. Contact me for further discussion @ email@example.com or 917-741-8294.