“Martha’s Vineyard is mostly sand. There is not a lot of rock.”
There is a lot of rock. Lots of big rocks. The island is mostly rock.
At the west end of MV it is rock.
Obama’s house is on salt marsh/pond. It is mostly sand around there. All of his utilities are BURIED. There are no electric lines running to the house in any pictures.
Plus they have an inground pool. Again, unless they blasted when they put it in originally. Which is unlikely.