Vieques is such a gem in Puerto Rico. A short inexpensive ferry ride away or even shorter plane ride away. My family has been to Vieques twice now and we always look forward to when we get to go back. One spot that we enjoy in particular is Playa Negro (black sand beach). You park in a small lot and cross the street and go on a 10-15 minute long winding hike that is fairly easy to navigate. The beach is beautiful with small cliffs surrounding it.
The black sand on the beach is very unique. It is almost like the kinetic play sand you would buy at the store. Clumps easily and is definitely very black. Probably the most unique sand I’ve ever experienced.