Nov 282011

Taking survey measurements in Tank Cave

About the site

I’ve talked about different dives in Tank Cave on multiple occasions. As well as being the longest cave available in my home region of Mt Gambier, it’s also very well suited to photography. With crystal clear water, shallow depths, tunnels that change from white walled, to black, to orange with sunken floors, air pockets, small flatteners and large chambers, Tank provides a great place to experiment with cave diving photography.

About the dive

The intention for this particular dive was to complete a more accurate wall profile of a room that’s approximately an 800m swim from the cave entrance. With JDZ carrying measuring tapes and survey slates and myself with camera and additional strobes we headed off down the tunnel. The dive involved travelling through a restriction known as the Goat Track that used to represent significant challenges to divers. Traffic and time have opened up this area so that divers with backmounted twins can pass fairly easily, and I felt my strobe would be safe strapped to the back of a sidemount diver.

Once we reached our destination in G tunnel, JDZ reeled out the tape measure around the wall while I scouted the locations. With limited time to gather all the data he needed, posing for photography wasn’t part of the plan. On the other hand, I knew he would be pausing each time the tape changed direction to take measurements. I moved around the cave ahead of the action, placing a further hand held strobe on the ground to light the background and waiting for my model to swim into the shot.Mapping the silt cloud in Tank Cave

About the shot

I had previously taken photos in the middle of this large chamber, without realising that the most interesting shapes and colours are around the outskirts. This particular tie off point is at one end, where the rock protrustion used for the tie off is a different colour to the surrounding cave. I like the contrasting colours and the lines created by the rock formations.

Unfortuantely the backmounted strobe hasn’t fired, with the sensor for it hidden behind JDZ’s left hand. The off camera strobe that I placed on the floor is lighting the background behind the diver and providing some shadows. JDZ is noting down distance measurements on the survey slate as his bubbles head up to the roof above.

As I discovered with previous “action” photography, action in caves means silt. For cave photography I much prefer to take photographs through water that hasn’t been swum through by a diver, giving crystal clear images. In this case there had been a previous lap to lay the measuring tape and the silt created by inserting the tie off is visible in the shot. While I might prefer silt-free shots, silt is a realistic representation of cave diving – you only have to check out the second shot to see how it can develop as you try to get a task completed.

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