Crystal Bay is Nusa Penida's best beach: a sheltered cove with clear water, good snorkelling directly from the shore, and a small island (Nusa Ceningan) visible across the strait. The bay is calm enough to swim in for most of the year, and the reef just offshore supports reef sharks, sea turtles, and schools of smaller fish. It is also the main base for dive operations on the island's northwest coast.
The village behind the beach has dive shops, a few warung restaurants, and some simple accommodation. The bay is the sensible base if you are staying overnight — it is more accessible than most of the island and positioned midway between the west coast viewpoints and the dive sites.