Meet the site
The Three Sisters is one of the most physically demanding cave dives in the Mount Gambier region, and one of the oldest documented – the cave has been known since at least 1933. It originally had three roof windows, hence the name, but today there is a single gated entrance a few metres off Glencoe Mile Hill Road near Tantanoola. Entry is through a 1 m concrete pipe followed by an 18 m vertical drop, climbed on a wire rope ladder with every person clipped to a belay.
At the bottom is a large talus mound – a cone of collapse debris, with glass fragments and other rubbish that fell through the windows over the decades – leading down into a dome chamber about 30 m in diameter. The main chamber reaches about 35 m. Beyond it the cave's notorious 'flattener', a restriction only 30-40 cm high that runs for several metres, is the reason the site is sidemount-only and graded Advanced Cave.
Rules are extensive and reflect both the vertical entry and the roadside location: helmets mandatory inside the cave, one responsible adult topside, a maximum of four divers in the water, one vehicle on the hard pan, hi-vis vests and cones, and the key collected from the Glencoe Post Office and Bistro. Wattle Range Council owns the site. The dive rewards fit, experienced Advanced Cave sidemount divers with a big, dramatic chamber and a genuinely committing restriction; for everyone else, the ladder alone should give pause. Allow a full morning for rigging and traffic management.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Three Sisters Cave is recorded as Cave/Cavern 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.
- Other water users
- Ask about vessel activity, exclusion areas and the agreed surface arrangements.
- Planned depth
- Confirm the intended route and training requirements; the recorded maximum is not a target.
- Overhead environments
- Ask whether the plan stays entirely in open water. A wreck or cave listing is not permission or training to enter.
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 Three Sisters Cave 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 Three Sisters Cave 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
Very little – occasional cave crustaceans
Location
A sidemount-only Advanced Cave site entered through a 1 m concrete pipe and an 18 m vertical drop beside Mile Hill Road near Glencoe/Tantanoola; a 30 m dome chamber to about 35 m.
Facilities nearby
None at site. Key, food and toilets at Glencoe Post Office and Bistro; 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.auRecord updated 26 Sept 2026. Source claims are being reviewed.