'It's more like poop, and it comes from the same place as poop.'

A couple in the UK are set to fetch an estimated $70,000 (Dh257,000) for whale vomit!

The couple chanced upon this seemingly filthy - yet rare substance - when taking a long walk on the beach and picked it up assuming it was a piece of rock, CNN reported.

According to Christopher Kemp, author of "Floating Gold: A Natural (and Unnatural) History of Ambergris", the rock could be ambergris, a rare substance used to make perfumes last longer on the skin.

"Ambergris is definitely not vomit," he told CNN.

Couple stunned after stumbling across chunk of WHALE VOMIT on beach - and it could be worth £50,000 pic.twitter.com/SF2Jb7T8UT - Heather (@itsrealH) April 13, 2016

"It's more like poop, and it comes from the same place as poop, but it's only made by a small percentage of sperm whales, as a result of indigestion."

The couple, Gary and Angela Williams, followed a pungent smell while walking on Middleton Sands beach near Morecambe Bay that led them to what they believe to be a large lump of ambergris.

"Ambergris feels a little waxy, and smells very complex: a mixture of dung and the ocean, and old wood, and tobacco, and moist earth, and ozone," Kemp said.

The substance, often called "floating gold," is produced only by a tiny percentage of sperm whales.

What makes this discovery noteworthy is the fact that ambergris can float in the ocean for decades until it eventually washes up on shore, where people find it.

Cautioning others who are seeking to make a quick buck by hoping to find this 'floating gold', Kemp says 'it's very hard to know if you've actually found ambergris, as it is extremely rare and found infrequently."

Kemp suspects that the couple's find may not be genuine ambergris, stating that while ambergris is waxy, the substance they found is "a little too waxy" and looks more like animal fat than ambergris, he said.

If it is genuine ambergris, the British couple's lump could be worth an estimated $70,000.

They are reportedly in negotiation with potential buyers in New Zealand and France.

Apparently, this is not the first time such a discovery has been made. Not very far back, in 2012, an 8-year-old British schoolboy found a 1.3-pound mass of it in the sand that was worth about $63,000.

Good, high-quality ambergris is worth thousands of dollars per pound, Kemp told CNN.

It is noteworthy that although the harvesting of ambergris isn't harmful to the whales, the trade of it is banned in the United States to avoid exploitation of the endangered species.

The story originally appeared here.