Mount Gambier · South Australia

Tank Cave

One of the longest underwater cave systems in Australia — advanced CDAA qualification only.

Cave & cavern
technical

Tank Cave is one of the most extensive underwater cave systems in Australia, with many kilometres of surveyed passage in a complex, multi-branch maze.

It is restricted to divers holding the highest CDAA qualification categories, and access requires both that qualification and landowner permission.

The navigation complexity rather than the depth is what makes it demanding — the system branches repeatedly and route-finding is a serious skill requirement.

Cave diving, represented by an AI-generated editorial image.

Max depth

20 m

typically 12 m

Access

shore

Current

minimal

Water temp

15–17°C

Level

technical

Depth range at Tank Cave, against standard recreational training limits. Route selection and conditions change the actual profile.

Diving profile

Region	Mount Gambier
State	South Australia
Access	shore
Site type	cave
Minimum depth	3 m
Typical depth	12 m
Maximum depth	20 m
Current	minimal
Visibility	Exceptional when undisturbed
Water temperature	Roughly 15–17°C
Experience level	technical

These are guidance categories, not guarantees. Conditions on the day, and an operator’s own requirements, override any classification here.

Marine life

Effectively none — this is a freshwater cave system.

Access

Highest CDAA category qualification required.
Landowner permission and booking essential.
Entry is through a small shaft.
Detailed survey knowledge is expected.

Hazards

complex multi-branch navigation
restrictions
silt-out risk
no direct ascent anywhere in the system
gas management over long penetrations

Operators servicing this site

Businesses documented as regularly diving this site. Only operators we have established a connection for are listed.

Dive ExperienceA Mount Gambier business serving the region's cave and sinkhole diving community, including equipment and gas support.

Training that is genuinely useful here

Not a list of everything available — the qualifications that actually change what you can do at this site.

Cave DiverFull overhead penetration diving, where direct ascent is not available at any point.Advanced NitroxHigh-oxygen decompression gases and oxygen-clean equipment — not ordinary recreational Nitrox.Decompression ProceduresPlanning and executing dives with a mandatory decompression obligation.Sidemount DiverCarrying cylinders at your sides — redundancy, streamlining and access through restrictions.

Technical background

Decompression DivingWhen the option of a direct ascent is deliberately given up, and what that changes.TrimixHelium in the breathing mix — and the gas logistics that determine whether a trip is possible.Cave Diving in AustraliaThe CDAA system, Mount Gambier, and why recreational certification does not apply.Sidemount DivingCylinders at your sides — redundancy, streamlining and restriction access.

Related dive sites

Worth reading alongside this one.

Kilsby's SinkholeA limestone sinkhole with water so clear the experience is closer to flying than diving.Piccaninnie PondsA karst spring of extraordinary clarity, with the Cathedral chamber and a chasm beyond 100 metres.Ewens PondsThree shallow spring-fed ponds connected by channels — a drift dive through crystal-clear freshwater.

Dive sites nearby

Other documented sites within range, nearest first — useful for building a trip rather than a single dive.

Kilsby's Sinkhole · 10 kmA limestone sinkhole with water so clear the experience is closer to flying than diving.Ewens Ponds · 27 kmThree shallow spring-fed ponds connected by channels — a drift dive through crystal-clear freshwater.Piccaninnie Ponds · 31 kmA karst spring of extraordinary clarity, with the Cathedral chamber and a chasm beyond 100 metres.

Location

Tank Cave, Mount Gambier, South Australia.

Frequently asked questions

How deep is Tank Cave?

Depths range from around 3 metres to roughly 20 metres, with a typical profile around 12 metres. Conditions and route selection change this considerably.

Is Tank Cave suitable for beginners?

It is better approached with experience beyond entry level. Parts of this site require technical training — decompression, overhead or mixed-gas qualifications. Discuss your recent diving honestly with the operator rather than relying on certification alone.

How do you get to Tank Cave?

Access is shore based. Highest CDAA category qualification required.

Is there current at Tank Cave?

Current is recorded as minimal. Conditions vary daily and should be checked close to the day.

What will I see at Tank Cave?

Commonly reported marine life includes Effectively none — this is a freshwater cave system.. Sightings are never guaranteed.

When is the best time to dive Tank Cave?

Conditions vary through the year. Visibility is exceptional when undisturbed. Check with local operators close to your dates.

Where is Tank Cave?

Tank Cave is in the Mount Gambier region of South Australia.

Last researched: September 2026. Dive businesses change frequently — confirm current services, prices and requirements directly with the operator before booking.