It was on Sydney Harbour this past Australia Day, in a boat heading into Circular Quay, and David Maidment couldn't believe his eyes: Sydney Rock Oysters, and plenty of them, covering parts of the sea wall around the Opera House.

Perfect. Two of Australia's best-loved occupants of the sea shore, one native, living and thriving on the other, a man-made structure.

For Mr Maidment, an oyster farmer up the river at Narooma for 35 years, it was a good sign.

"It was low tide and we went past the Opera House, in one of the boats that was in a procession," he said.

"It's covered in rock oysters.

"Once upon a time, 15 years ago, it was very unfavourable for growing oysters at all in Sydney Harbour. I think the clean-up work that's been done in Sydney Harbour has enabled the larvae to settle again.

"It's just a massive catch on the concrete balustrade that run down to the water. That's a good sign of a healthy waterway."

Patience is a virtue for any primary producer, and they also need help from things they can't control - in this case, contaminants need to stay out of the water.

The shellfish are cultivated from the beginning of their life, when farmers place plastic crates or tubes in parts of the river known for good falls of "spat" - fertilised larvae. These are about 65 microns across when first fertilised, and they use tiny cilia (hairs) to move up and down through the water. After a few weeks, they settle.

"They've grown considerably in 21 days, gone through a number of stages, they've gone through hormonal changes when they want to look for somewhere to settle, form a shell, and move out of this free-swimming larval stage," Mr Maidment said.

The crates are left for six months, long enough for the spat to grow into oysters.

"They've got a shell and they're little baby oysters about the size of your fingernail, and you can grow them up."

These are then moved to larger structures in the water, called leases, to give them room to grow. Over the next few years, the slow-growing rock oysters will be harvested, graded and returned to the lease until they are large enough, with 3-5 million oysters on Mr Maidment's leases at any time.

"In two years, 2½ years, you've got animals that are big enough to sell," Mr Maidment said.

"They are fairly slow growing but there is a good side to that. Even though they take longer to mature and cost more to produce them, they've got a much more delicate flavour.

"They only feed on certain size algae ... and they take a little longer to grow because of that."

The cleaner the water, the easier to grow oysters.

Oysters are susceptible to too much rain, or not enough rain and everything the rain washes into the river.

Certain bacteria can destroy a whole year's crop - or more. Such has been the fate of some growers on the Hawkesbury River and Port Stephens areas over recent years.

These are not problems that have beset South Coast oyster growers.

"Like all the southern rivers down here, with the lesser population, less pressure on the waterways, there's less issues with growing oysters."

Narooma Oyster Festival - April 5-6

The first thing you notice when you arrive in Narooma is the turquoise water flowing under the bridge up towards Wagonga Inlet.

Coming in from the north (it’s a touch over 3 hours from Wollongong), a sharp corner opens up to reveal the stunning clear expanse, fishers dotting the water, rustic seafood businesses on the edge of the shore.

Soon afterwards you start to notice bumper stickers on cars saying ‘‘Narooma – how life should be’’. And it’s easy to nod in agreement.

The best of the coast will be on show early next month as the Narooma Oyster Festival is held.

As local farmers know, the South Coast of New South Wales is one of the very best places to grow oysters on this planet.

So each year they invite the rest of the world to come and have a taste. Held over two days, the main event on Saturday April 5 is the Naturally Gourmet Fair on the edge of the inlet.

Running from 10am-7pm, the fair features a range of food and craft stalls. Chefs from fine restaurants along the coast hold cooking demonstrations – David Campbell from Nowra’s Wharf Road restaurant, Huw Jones of Zanzibar Merimbula, and Josh Tyler from Tyler’s Pantry at Mogo.

A shucking competition, oyster cooking masterclass and mobile shuckers opening oysters on the spot will add to the atmosphere.

Oyster farmers have been working on ways to attract more visitors to what the locals already know is world-class produce.

Visit naroomaoysterfestival.com for more festival details.