Meet the site
One Tree is a large, deep farm sinkhole in the Mount Schank field, known mostly to CDAA members. The association's listing is short: large deep sinkhole, visibility usually good below 20 m, thermoclines, a harvester and some rubbish. Like many of the region's farm holes it was once used as a convenient place to dump unwanted machinery, and the old harvester on the bottom has become a landmark.
The dive profile is typical of the Mount Schank sinkholes: the upper layer is often greener and murkier, then one or more thermoclines mark the change to colder, clearer water below 20 m, where the walls and the depth of the hole open up. The open daylight zone makes it a Basic Cave site, and the depth means that narcosis and gas planning deserve attention even without an overhead.
What distinguishes One Tree is its old-fashioned access. There is no online booking – divers call at the house, show a CDAA card, sign the logbook and collect the keys, and the rules are explicit that if nobody is home or you do not have your card, you do not dive. That makes it a site to plan with a phone call and some flexibility. Exact depth and dimensions are not published. It suits CDAA Basic Cave divers looking for a quieter, deep sinkhole with a bit of agricultural archaeology on the bottom. Because access depends on the landowner being at home, many divers treat it as a back-up option on a Mount Gambier trip, calling ahead in the morning and diving if the family is around. Visiting divers should leave gates as found, keep clear of stock, and thank the owners – the future of farm access across the region rests on that goodwill.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
One Tree is recorded as Sinkhole/Cenote in Mount Gambier Sinkholes & Caves. The listed access is shore. Confirm the actual meeting point, route and permission to visit; a map pin does not establish any of these.
Topics flagged by the stored research
These are questions prompted by the existing notes, not a verified or complete hazard assessment.
- Lines and obstructions
- Discuss any known entanglement concerns and the suitability of the planned area.
- Planned depth
- Confirm the intended route and training requirements; the recorded maximum is not a target.
Historical access notes exist for this record, but have not been independently verified for current use. Request current directions from the operator or site manager rather than following an old entry description.
Questions, answered
Is One Tree suitable for my certification?
The record lists Cave/Cavern certification. That does not establish suitability for every route or day. Share your training, recent experience and equipment needs with the operator and ask about the specific proposed dive.
Can I book One Tree through YouDive?
YouDive is an independent research directory. Contact an operator directly to confirm whether it currently runs the trip, the inclusions and the booking terms.
What you might see
Little recorded – algae in the shallows, occasional yabbies
Location
A large, deep sinkhole on the LG McKinnon & Sons farm at Mount Schank, south of Mount Gambier, with thermoclines and good visibility below 20 m.
Facilities nearby
None – farm parking. Fills in Mount Gambier.
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
cavedivers.com.aucavedivers.com.auscuba.comRecord updated 26 Sept 2026. Source claims are being reviewed.