Piedra Bermeja is an outside-reserve El Hierro dive that runs over sand and rock toward the roques, circles a wall on the open-sea side, and returns through a narrow passage. It is a boat dive from La Restinga with a scenic wall-and-rock feel, mixed fish life, and a route that rewards steady buoyancy, relaxed trim, and a guide who can read the exit corridor. The site is more about natural rock structure, open water, and pelagic movement than about dense coral gardens, so the planning feel is classic boat-diving terrain rather than a casual shore stroll.