Ambergris is often smoothed by the ocean (Image: ambergris.co.nz)

Leon Wright and his wife took home a 14.75kg lump of ambergris, found in the innards of sperm whales and used in perfumes after it has been vomited up.

Sought after because of its rarity, ambergris can float on the ocean for years before washing ashore.

Worth up to $20 a gram, Mr Wright's find on a South Australian beach could net his family US$295,000 (£165,300).

At first, Mr Wright and his wife Loralee left the strange lump on the beach where it was found.

However, two weeks later the couple returned to Streaky Bay and found it still lying there.

Floating gold

Curious, Mrs Wright persuaded her husband to take it home.

AMBERGRIS FACTS Found in warm water oceans around the world Bile secreted by sperm whales as a digestion aid Solidifies and floats on water, sometimes for years Used in perfumes, medicines, flavourings Banned in US under endangered species legislation

"I immediately decided it was ambergris - it couldn't be anything else," Mr Jury told Australia's ABC radio.

Mythologised for thousands of years, ambergris has been referred to as "floating gold" by scientists and scavengers who long for a windfall amid the surf.

Expelled from the abdomen of the giant sperm whale, often while hundreds of kilometres away from land, ambergris is a natural excrement thought to be used by the whale as a digestion aid.

The hard beaks of giant squid, a main source of food for the whale, have often been found inside lumps of ambergris.

Initially, ambergris is a soft, foul-smelling waste matter that floats on the ocean.

But years of exposure to the sun and the salt water of the ocean transform the waste into a smooth, exotic lump of compact rock that boasts a waxy feel and a sweet, alluring smell.

"It's quite remarkable when you think about it, because when the whale throws this out, it's discarded material that they can't digest," Mr Jury explained.

"[But] after 10 years, it's considered clean and all you're getting then is the wonderful musky, very sweet perfume, which I've got to say is ultra smooth - it's unbelievable."