Just southeast of Kailua, Lanikai is an exclusive residential neighborhood fronting a gorgeous stretch of powdery white sand overlooking two postcard-perfect islands, known locally as the Mokes. Today the beach is shrinking: nearly half the sand has washed away as a result of retaining walls built to protect the neighborhood’s multimillion-dollar mansions. There are 11 narrow public beach-access walkways off Mokulua Dr. No bathrooms, no lifeguards.