Tourism business grows alongside prime lambs at Kilsby Sinkhole

And the farm owners have been building on this tourism interest, with accommodation and gin now included.

There are more than 50 sinkholes along the Limestone Coast, but the privately-owned Kilsby Sinkhole has a unique offering, with snorkelling and site tours, scuba diving and free diving available.

Five generations of the Kilsby family have farmed the land at Moorak, just south of Mount Gambier, while the more recent history of the sinkhole has included a watering hole on a stock route, childhood playground, a source for local irrigation and a site of secret weapons testing for the government.

Graham Kilsby believes the beauty of the site requires it get shown, leading him to invite in divers a little more than a decade ago.

But it was the rising cost of insurance that led to him building on the tourism business about six or seven years ago.

"I used to notify our insurance companies that we had the sinkhole and free divers," he said.

"Then one year, the insurer said they couldn't provide a public indemnity insurance to the farm if the sinkholes were there."

While there was an option to lock the sinkhole away, Mr Kilsby went another way, and instead divided the sinkhole area away from the farm property, so it sat on its own title.

That allowed him to get insurance for the farm, but the high premiums associated with the sinkhole meant they needed to get more revenue, so he began guided tours of the site.

"It is beautiful and I think it would be really disappointing if it just closed," he said.

"I enjoy seeing people come here and enjoy it, from school groups to 80 or 90 year olds.

"It was a lot of work but I'm happy we kept it open - we get thousands of people through every year.

"People want to see them, experience them and know they are there."

Alongside the tourism business, Mr Kilsby operates a 950 hectare farm - 340ha owned and 610ha leased, which is used to run 2700 composite ewes for prime lamb production.

This includes 48ha of land under pivot irrigation to finish the lambs during summer - using water from the sinkhole.

His partner in the tourism business, and fiancee, Jo Feast, also runs her own Angus and Hereford beef and Merino wool operation at Green Point, along the SA coast, near the SA/Victorian border.

But as the tourism steps up, the next generation is stepping up to take on the farming, with Mr Kilsby's sons Adam and Robert taking on his farm while Ms Feast's son Morgan will take on the southern property.

Mr Kilsby said having the diverse income from tourism allowed them to keep the farming side strong.

"If I didn't have this business, I don't know if I could have both sons home to the farm," he said.

The latest project at the Kilsby Sinkhole is nearing completion, with construction nearly finished on four villas, just metres away from the sinkhole, which can sleep 20 people between them.

"I had always wanted accommodation here, probably not the extent we have," he said.

Another project has been the development of the Sinkhole Gin, which has recently shifted to be made on-farm.

Mr Kilsby said the initial idea for the gin came from the divers who visited.

"The divers always said the water at the sinkhole was as clear as gin, so we thought 'let's run with it'," he said.

For several years, as they worked out if the venture would work, the gin was made in Melbourne.

But once it was proven a success, they invested in the infrastructure on site, working with an experienced distiller with Mr Kilsby also learning the ropes.

"It's wonderful taking water from the sinkhole and distilling gin and limoncello right on the edge," he said.

The gin is sold in local bottle shops and restaurants, with some outlets in Adelaide.

Mr Kilsby said they would also push further into Melbourne markets as they built on this facet of the business.

Developing the gin also helped inspire another side project, with it flavoured with a native berry that grows along the SA and Victorian coast - muntries.

In order to secure supply of the fruit, the Kilsbys planted six, 70 metre rows along trellises.

This has also grown, with them supplying wholesale markets in Adelaide as well as local restaurants.

"They're quite sought after as can be rare," he said.

The plants are sown on an ancient sand dune and irrigated with water from the sinkhole.

"The sandy and unfertile soils, that is what they love," Mr Kilsby said.

"They won't grow or fruit on heavy soils.

"This year the trellises are loaded with fruit."

Mr Kilsby said, while there had been quite a few projects, as well as some others in the pipeline, it had all been done at a manageable level.

"A lot has been done but we have done it in stages," he said.

"We've got something operational and running well before the next stage."

He is passionate about encouraging people to visit the Limestone Coast, and about the potential for agritourism.

"I think the more people we have doing unusual things, the more reason for people to come to our region," he said.

"We have so much on offer in the Limestone Coast."