Meet the site
The Shaft is Australian cave diving's most historically important site, and one of the most dramatic sinkhole dives anywhere. From the surface it is almost nothing – a hole about a metre wide in a farm paddock at Allendale East, discovered in 1938 when a horse stumbled into what was then a foot-wide opening, later enlarged for access. Below it lies an enormous flooded chamber roughly 140 m long and 80 m wide, with the water surface about 7 m below the paddock. A central rockpile rises to about 36 m depth, a northwest tunnel reaches 80 m and an eastern tunnel descends to 124 m; CEGSA divers mapped it in detail and surveyed those depths.
The name comes from the column of sunlight that, around midday, drops through the narrow entrance and strikes the rockpile – a spotlight in a void so big that even a 200 W video light cannot illuminate the walls. Visibility is typically excellent, and the effect of floating in black water with a single beam of daylight is unforgettable.
On 28 May 1973 four divers – Stephen and Christine Millott, Gordon Roberts and John Bockerman – went beyond their planned limits without a guideline, became lost and drowned; their bodies were recovered between January and April 1974. The tragedy led directly to the formation of the Cave Divers Association of Australia in September 1973 and to the controlled-access, graded system still in force. The site was closed, successfully mapped in 1984 and later reopened by arrangement with the landowner.
Access today is tightly controlled: CDAA members only, on supervised dives run by approved, insured Dive Supervisors. Basic Cave divers stay around the rockpile top within 40 m; the deeper tunnels are trimix territory. It suits well-drilled CDAA divers comfortable with vertical entries and very large, dark spaces.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
The Shaft 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.
- Water movement
- Ask how swell and local exposure affect the proposed entry, exit and route.
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 The Shaft 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 The Shaft 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
Essentially none – bare limestone and rockpile; occasional small crustaceans
Location
A huge underground flooded chamber (about 140 x 80 m) entered through a 1 m hole in a paddock at Allendale East, about 20 km south of Mount Gambier; surveyed to 124 m.
Facilities nearby
None – paddock parking only; bring winch/ladder, ropes and harness as required. 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
en.wikipedia.orgcavedivers.com.audivedb.netcavediving.net.auscuba.comRecord updated 26 Sept 2026. Source claims are being reviewed.