Allendale Sinkhole Australia

Discover the fascinating geological wonder of the Allendale East Sinkhole, a distinctive feature in the heart of this small township. As the main Mount Gambier-Port MacDonnell “Bay Road” gracefully splits, this sinkhole captures attention with its 10-meter diameter collapse and a steep descent leading to a mesmerizing crescent-shaped pool, situated 6 meters below ground level.

  • Region: South Australia
  • Coordinates: -38.005152, 140.708572
  • Depth:
  • Remarks:
  • Type: Cave

Underwater Exploration: The Enchanting Realm Below

For adventurous recreational cave divers, the underwater region holds a captivating single passage, spanning 35 meters and descending to a maximum depth of approximately 28 meters. The entrance lake, likely extending beneath the road, provides a unique subaquatic landscape awaiting exploration. A smaller dry crawl-down passage under the north-eastern wall adds an additional layer of intrigue to this underwater wonder.

Subdued Beauty: Clear Waters in the Shadows

Although the water boasts exceptional clarity, the absence of direct sunlight renders it quite dark. Despite the lack of vibrant aquatic life, the sinkhole reveals some unique inhabitants, including syncarids and yabbies, with at least one strikingly pure white yabby. In 1981, water samples indicated a moderate nitrate level of 17.1mg/l, while detailed mapping by Stan Bugg and Brian Cornell of SAUSS (Inc) in the early 1990s further unveiled the sinkhole’s intricate structure.

Historical Significance: A Well-Known Watering Hole

Allendale Sinkhole has a rich history dating back to the early 20th Century, serving as a vital watering hole for bullock wagons. An intriguing anecdote from the August 3, 1971 edition of the “Border Watch” newspaper recounts the mysterious appearance of the cave after a bullock wagon’s departure, with both the team and teamster reemerging at Eight Mile Creek. Father Julian Tenison-Woods’ “Biological Observations” of 1862 also alludes to the presence of a bullock team and dray in the vicinity.

The Filling Saga: Tales of Rock Dumping and Persistence

Early attempts to fill the sinkhole, recounted by Mr. W.A. Habner, involved substantial efforts with large basalt rocks and countless truckloads of loose paddock-stones. The saga continued until an astounding NINE THOUSAND CUBIC YARDS of rock were deposited at the entrance, admitting defeat only when the cave reopened. Despite extensive records, no evidence of pre-fill scuba dives has surfaced to date, highlighting the sinkhole’s mystery in the context of regional exploration.

Allendale Sinkhole Australia


What is the water temperature inside the cave?

The water in the Allendale East Sinkhole is warm, particularly during the summer months, providing a comfortable environment for divers.

Is the water clear in the Allendale East Sinkhole?

Yes, the water clarity ranges from 3 to 6 meters, offering excellent visibility for divers eager to explore the submerged passages and features.

Dive Right In Scuba
Underwater caves