I wax lyrical about Port Noarlunga Reef at every opportunity. It is not only one of Adelaide’s closest dive sites but also amazingly diverse in what can be experienced.

One of my favourite dives here is in the deep gap that separates the north and south sections of the reef. Simply called ‘The Gap’, a complex maze like structure of limestone bommies, makes its way south from the northern reef section down to a sandy, silty base around 16m before climbing back up to the southern reef section.

The Gap is a wonderful place to explore full of large limestone boulders adorned with sponges, gorgonian corals, and algaes. Large schools of silver drummer and white trevally dazzle while big dusky morwongs more than a meter in length raise the heart rate just a little as they appear out of the gloom or from behind bommies. The gap is also a great place to get completely lost unless you are diligent with good compass work.

At night a dive in the Gap takes on an eerie other worldly nature. Bommies become giants with manes of flowing kelp lurking in the dark. Every flash and flicker of silver in the distant light of the torch-beam makes my heart skip a beat or two. The sand is alive with molluscs while littered remains of crab mark the last meals of a nearby octopuses.

On Sunday night’s dive I found nestled in a challis-like sponge this beautiful black cowrie with its shell of mottled gold. So named ‘black’ as their black mantle hides the polished shell beneath. This one is feeding on the algae that covers the cup of the sponge. I have noticed cowries feeding like this in bowl like sponge structures on previous dives. Perhaps the silt collect down deep in the gap promotes the algal growth and attracts the cowries.

I finished the dive with the long swim back to the jetty, to fresh air and to the quizzical looks of passersby as I emerged from the inky black water in the torchlight. If only they knew what was down there. Gold!