Sailboats and small pleasure craft float in front of historic Twenties and Thirties homes. Neighbors enjoy leisurely sunset walks along the water. One of South Florida's myriad gated communities? Try again. An affluent, private residential island sandwiched between Miami Beach and the mainland? Nope. Would you believe unincorporated Miami-Dade County? It's true. This eight-square-block area, located between NE 87th and 91st streets, NE Tenth Avenue and Biscayne Bay, offers a unique twist on waterfront living. Instead of facing the bay, homes sit on "Lake Bel Mar," which according to folks in the area is the only canal in Miami-Dade County located in front of a row of homes. The place is so charming, secluded, and quiet that residents begged us not to tell people about it. Sorry.