Wonky hole

A Wonky hole is the Australian term for submarine freshwater springs on the seabed in the Great Barrier Reef and the Gulf of Carpentaria of Queensland. Wonky holes can be found in the coral reef up to 60 km offshore.

Wonky holes are located along riverbeds which existed in the last glacial period ending about 11,000 years ago. At that time of the last glacial maximum much of northern Europe and North America was covered by ice sheets up to 3 km thick; the water tied up in the glacial ice lowered the sea level more than 120 m. The sediment in the submerged river beds from that period has been covered with coral in many places. Since the sediment is more permeable than the surrounding materials, it channels fresh water to thin spots in the coral, creating the fresh water springs called wonky holes.