Ambergris is a very posh name for a type of whale excrement — whale poo — and it's extremely valuable.
It was initially believed ambergris was whale vomit, but later research has confirmed it actually comes out the other end.
It's the bits and beaks sperm whales don't digest. Some find their way into the intestine and after several years fermenting, exit the bowel and wash up on beaches.
They're collected and then extracts are put into expensive perfume.
The floating gold is highly valuable, selling for nearly $50 per gram.
It's been found around New Zealand's coastline, including Aramoana in Otago, but you have to smell a lot of fakes to find the real thing.
Otago Museum has a collection of ambergris and people will sometimes bring in suspected samples for checking, according to curator Kane Fleury.
"It'd be about once or twice a year we'd get a spate of people thinking they're bringing what they've found is treasure into the museum," he told Seven Sharp.
"In my time at the museum, we have not had any real ambergris brought in."
Instead, it's more likely people are bringing in what he nicknames "ambergris not" — dog poo.
"It's pretty rare stuff. The ones that know what it is are not the ones bringing me dog poo," he said.
The best places to find ambergris are a closely guarded secret, but Fleury was prepared to reveal some of his tips.
"You're looking at any beach which gets a large amount of swell action and some good strong currents, and probably the best time to go out there looking is probably after a nice high tide, after a full moon."