Tea Tree is the second of the two Penola Park Estate sinkholes at Wye, alongside Horse and Cart. The CDAA's description sets expectations clearly: eight metres of ladder required, water cold and dark, much tree debris, shallow silty floor, eels. It is graded Basic Cave.

Unlike the big open sinkholes of Mount Schank, Tea Tree is small, shaded and gloomy. Light struggles to reach the water, the floor is shallow and covered in fine silt, and branches and trunks have accumulated over the years. The eels are the resident attraction – short-finned eels are common in the region's springs and sinkholes and here they hide among the timber. Visibility depends entirely on how gently the first diver moves; a couple of careless kicks turn the water brown.

For most divers it is a novelty rather than a destination: an easy phone call or email to the owners, a ladder descent, and a short exploratory dive that can be combined with Horse and Cart on the same visit. It is also a reasonable place for Basic Cave divers to practise buoyancy and trim in poor visibility without any overhead. Bring a good primary light even though it is technically an open sinkhole, and be ready for cold – shaded water feels colder than it is on long, slow dives.

Private-owner goodwill keeps sites like this available, so follow the owners' instructions, leave gates as found and carry out any rubbish. Combine it with Horse and Cart for a relaxed morning on the estate.

Arrange access at least 24 hours ahead with landowners Dale and Heather Perkins, Penola Park Estate (0438 854 724, lizzie@penolapark.com.au). The property is at Wye, south-east of Mount Gambier towards the Victorian border (about 25-30 minutes' drive; Horse and Cart is at 117 ACI Road on the same estate). Park as directed, carry gear to the sinkhole and rig or use 8 m of ladder to reach the water; lower cylinders separately.

Unaffected by swell or tide. Access and surface conditions on private farmland are the limiting factors: Total Fire Ban days may restrict access or compressors, summer heat makes vertical exits hard work, snakes are active in warm weather and winter rain turns farm tracks muddy. Underwater conditions are stable, with groundwater at a constant ~15°C.

The sinkhole is shaded and dark even on bright days.

Descend the ladder, stay neutrally buoyant above the shallow silty floor, explore the margins among the tree debris looking for eels, and exit before the silt catches up with you.

CDAA grade: Basic Cave (5L128), owners Dale and Heather Perkins. Arrange ≥24 h ahead. Primary light recommended; no overhead.

No operator – CDAA Basic Cave members arrange directly with the landowner.