Snell’s window in Piccaninnie Ponds

About the site

I’ve previously talked about diving in Piccaninnie Ponds, and I’m about to again. Unlike other caves where I’ve had to work to find different angles on photos, the Ponds seem to be photogenic from every angle. The stunning blue, green and white colours, the clarity of the water, and the chance to contrast sunlight with the darkness inside the Cathedral create photographic opportunities everywhere you look.

About the dive

On this particular day, we’d booked permits to get in early in the morning for the best water clarity, and closer to midday for the best sunshine. The Chasm in the Ponds runs roughly North-South, so early and late in the day the angled sunlight tends to get cut off by the walls. I’d noted the mostly blue sky and sunshine without really thinking too much about the fluffy little white clouds – these turned out to be the biggest gift of the weather on this occasion.

On the first dive we’d descended into the Chasm, for the second we dived into the Cathedral. Coming out of the Cathedral, the sunlight through the water was stunning. Thinking I was done with photography for the dive, I decided it was a good time to do a few barrel rolls through the shallows. Halfway through the first one, I realised the best photos were yet to come – the little white clouds in the sky above showed up beautifully from 15m under water.

About the photo

This shot takes advantage of the phenomenon known as Snell’s window. It’s noticible when you stand over a water surface and look down – beyond a certain angle, you see reflected light rather than seeing below the surface. The same applies from underneath, and when taking a photograph directly up there’s a circular boundary where the reflection starts.

As you can see in the second photo, if you create your own window from features on the dive, the circular effect of the window is much less noticeable. When that’s not possible, Snell’s window can be a great tool for adding a borderline and to draw attention to your subject. Despite normally preferring to put my divers on the thirds lines, in this case the symmetry of the window appealed, and I moved to create a centrally posed shot.

Having done this dive in multiple different conditions, my favourite thing about this photo is the clouds. Clear blue skies can look exactly like clear blue waters, and white cloudy skies often reflect even more light to create a huge highlight blowout from underneath. Little white clouds in a blue sky are unmistakable, and from 15m down they tell a great story about just how clear the water is. The surface conditions were also still and calm, meaning the only ripples on the surface were from our bubbles rising out.

There are a few challenges associated with shooting up. In clear water and without a point of reference like a horizon, it can often be hard for the viewer to tell which direction the camera was pointing. Diver silhouettes can end up in strange arrangements from underneath, and unless you want an artistic effect, the photographer needs to keep their bubbles out of the shot. The usual requirement for good buoyancy and situational awareness holds doubly true when you’re upsidedown and trying not to breath out at the wrong moment.