Molyneux Bay is a broad, shallow coastal bay on the southeast coast of New Zealand's South Island, encompassing the mouth of the Clutha River / Mata-Au and extending south to Nugget Point / Tokatā. The bay is characterized by a significant offshore sediment deposit known as the "sand wedge," a 6500-year-old accumulation of Clutha River material that shapes the seafloor. This creates a large, shallow area where depths remain below 20 meters for up to 15 kilometers from shore, influencing both marine habitat and angling opportunities. The bay is a known open-coast surf and boat fishery, with its dynamics heavily influenced by the river's discharge and coastal processes.