The Mt Gambier region of South Australia is famous for its many caves and sinkholes, but Tank Cave stands out from the crowd and is the crown jewel when it comes to cave divers. Tank Cave, so named because a water tank used to rest just above the top of the entrance, is an extensive maze-like system with over 7 km (23,000 ft) of passage making it one of the longest caves from Australia.
The Tank Cave entrance is on private property and access to the site is strictly controlled by the Cave Divers Association of Australia (CDAA). The complicated nature of the system (it looks like a crazy spider web) requires a strict familiarization process that allows cave divers to get to know the cave step by step. While there are many hoops to jump through before allowing access to the site, on the plus side this means that every cave diver is intimately familiar with all of Tank Cave’s main passages before venturing into the many side tunnels.
Sometimes cave divers worry that Tank Cave will turn out to be a big disappointment after all the fuss leading up to the first dive, but even gold line dives are quite exciting. Tank Cave, like no other in the Mt Gambier region, is a true gem and a joy to dive into. The cave is impressive, it’s relatively shallow (a maximum depth of around 20m), there is no flow to fight and the water is crystal clear, you really can’t go wrong.
However, the best part about diving Tank Cave is that there is still so much potential for exploration. While most people assume that everything around the Mt Gambier region has been found and discovered, this is definitely not the case and certainly not the case in this cave. My second weekend there, while still doing familiarization dives, my buddy and I found a passage just off the gold line. It was a small hole but the tunnel was clearly gone. At first, my friend couldn’t get past the restriction, so he waited patiently for me while I went to see what was beyond the squeeze. In the end, I laid almost 1,000 feet of line, so there are clearly a lot more new cave passages in Tank Cave.
This new section comes off the end of the C line and is definitely a side-mount only passage. Depending on its size, a tank may need to be removed to get past the initial restriction. However, the fitted parts do not end with the first restriction; there are several of them before you finally come to a larger, more open passage. The walls and ceiling, to begin with, are quite soft and squishy, meaning large chunks of the ceiling fall on you as you exhale and visibility quickly drops to zero. Not only is this a hazard when getting back out through the small restrictions, but it also means that this section of the cave is particularly fragile and needs to be handled with a little TLC.
To improve the quality of the survey, I called in Ken Smith, the legendary ‘Pinger Man’. The pingers are part of an underwater radiolocation system that allows the location of the pinger to be located underwater from the surface. This helps establish an accurate position for each GPS-accurately tagged surveying station, and as such helps link remote sections of the cave to the existing map. We pinged four spots that weekend and as such an accurate map will be released.
The exploration continues into Tank Cave at the end of a series of tunnels, making this cave an exciting one to visit and top of my list when heading to Mt Gambier. I am sure you will hear more about this cave as there are still many discoveries to come. Perhaps one day the cave will break the magic mark of 10 km (33,000 ft).