Kilsby Sinkhole

Kilsby Sinkhole Dive Site Guide | Mt Gambier, SA, Australia

By ScubaDownUnder Team · 2026-04-14

# Kilsby Sinkhole

A privately owned limestone sinkhole on a working farm near Mt Gambier, holding some of the clearest fresh water in Australia and plunging to over 60 metres.

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## Quick stats

| Detail | Info | |---|---| | Location | Mt Gambier, SA | | Skill Level | Advanced | | Depth Range | 0–60 m | | Typical Visibility | 40–60 m | | Water Temperature | 16–17 degrees C | | Best Season | Year-round, conditions are essentially constant | | Entry Type | Shore | | Hazards | Advanced Open Water minimum; Open water certified divers are restricted to 20m; Cave environment: overhead section requires cave diving certification for penetration beyond the open water zone | | Facilities | Parking area on the Kilsby family farm property; Basic amenities at the entry point, no change rooms or showers; Nearest full facilities in Mt Gambier |

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Standing at the rim of Kilsby Sinkhole and looking down into the water is a genuinely disorienting experience. The clarity of the water is such that the full depth appears to be visible from the surface, the pale limestone walls descending through the water column, the blue deepening toward aquamarine toward something darker below, and the occasional fish suspended in the middle of it all, casting a shadow on the bottom far below. This is 40 to 60 metres of visibility in a sinkhole on a sheep farm, and it is one of the most remarkable dive sites in Australia.

The Kilsby Sinkhole sits on private farming property approximately 20 kilometres southeast of Mt Gambier in South Australia's limestone country. The region sits above the Gambier Limestone karst system, a porous aquifer that fills the sinkholes, caves, and ponds of the Mt Gambier region with exceptionally clear, mineral-filtered groundwater. The sinkhole was created over millennia by the collapse of limestone ceilings above the underground water system, and the result is an open-sky pool approximately 40 metres across at the surface, narrowing as it descends. The Kilsby family have operated the site as a managed dive venue for decades, charging entry fees that fund access improvements and maintenance of the site.

The dive environment at Kilsby is unlike anything else in Australian diving. Entering via a series of steps and a ladder at the northern rim, divers descend into water that is 16–17°C year-round, the underground aquifer maintains a constant temperature regardless of season. The walls are pale limestone, textured and layered, dropping vertically to the main chamber below. In the upper section of the sinkhole, down to around 15 metres, ambient light from the open sky penetrates the water with a quality that produces an otherworldly blue illumination, no torch is needed in this zone, and photographers regularly cite the light in the 5–15 metre band as among the best they have worked in. Below 20 metres, natural light fades progressively and a torch becomes necessary, at which point the limestone wall textures and any submerged formations become the primary visual interest.

The endemic freshwater galaxias fish are the only marine life in the conventional sense, small, slender, schooling fish that occupy the mid-water column in loose groups. They are untroubled by divers and can be closely observed. The simplicity of the ecosystem is not a limitation but a feature: the absence of marine complexity throws all focus onto the architecture of the sinkhole itself and the extraordinary quality of the water.

Depth and certification requirements are clearly defined and non-negotiable at this site. Open Water certified divers are restricted to 20 metres. Advanced Open Water certification allows dives to 40 metres. The sinkhole extends to over 60 metres and connects via a cave system to the broader groundwater network, but penetration of any overhead environment beyond the main shaft requires cave diving certification, this is enforced and represents an absolute ceiling for recreational divers. The cave system is not a shallow exploration; these are serious technical environments.

Visibility is the statistic that defines Kilsby, and it is as extraordinary as reported. On a typical clear day, 40–50 metres of horizontal visibility is standard, and 60 metres is achievable in optimal conditions. The water is fresh and colourless, there is no tannin staining, no algal bloom, and no particulate matter unless someone has disturbed the silt near the walls. Buoyancy discipline is therefore doubly important: a careless fin kick near the limestone walls can produce silt clouds that will persist in the still water for the remainder of the dive and ruin the experience for every diver who follows.

The constant 16–17°C temperature demands a wetsuit capable of managing extended cold. A 7mm suit is the minimum for comfort on a standard dive; semi-dry or drysuit is preferred for divers planning multiple dives or extended bottom time. Dry suit training is available through Mt Gambier operators if required.

## Site Access and Logistics

The Kilsby Sinkhole is approximately 20km southeast of Mt Gambier via the Penola Road and local farm tracks, a map and GPS coordinates are provided by the Kilsby family upon booking. Entry requires pre-booking and payment of the access fee directly with the landowner. The site operates on a strictly managed capacity to avoid overcrowding.

Advanced Open Water certification is recommended for all divers; Open Water certified divers must remain at or above 20 metres. Cave diving certification is required for any penetration of the horizontal systems. A torch is required for dives below 20 metres. Tanks can be filled in Mt Gambier before departure. The narrow ladder entry and exit requires some physical agility, discuss this with the operator if there are any mobility concerns.

Mt Gambier is accessible from Adelaide (450km via the South Eastern Freeway) or from Melbourne (460km via the Princes Highway).