Batu Bolong, Nusa Penida is a boat dive around a dramatic rock arch on the island's south coast. The route starts on the coral rock, then wraps a steep wall and terrace before an offshore pickup, so it feels active rather than relaxed. It is an advanced site because tide, swell, and current decide whether the entry stays manageable, and the wall can hold dense fish life, turtles, sharks, rays, and macro when conditions line up.