Liang Beach, often called Hunimua Beach, is one of Ambon's better beach outings. The sand is pale, the water is usually clear, and the setting on the island's northeast coast feels less urban than the beaches closer to town.
Facilities are simple, which is part of the attraction if you come prepared. Bring what you need for shade, snacks, and transport back, and ask locally about swimming conditions before going far from shore.