Canadian salvage divers are searching for an unusual treasure - a vast hunk of sunken cheddar cheese.
Cheese producers strive for perfection - but usually on dry land
Cheese-maker Luc Boivin threw 800kg (1,700lb) of cheese in the Baie des Ha! Ha! in Quebec late last year, believing it would improve the taste.
However, food hygiene inspectors say Mr Boivin cannot sell his cheese without rigorous health testing.
And before it can be tested or sold, it must be found, and divers have so far failed, in the 40m (130ft) deep lake.
Mr Boivin's divers hope to satisfy the food standards authorities by finding the cheddar and taking samples from the cheese during its ageing process on the lake floor.
He suspects that the increased pressure and low temperatures at extreme depths accelerate the cheese-ageing process while keeping it perfectly cool.
"A few years ago, a fisherman came to us and said he'd found a piece of Boivin cheese at the bottom of a lake where he'd been diving," Mr Boivin told the AFP news agency.
"He took it, hesitated, ate it and told us it was one of the best cheeses he'd ever eaten."
His unorthodox decision aroused the ire of Canada's food standards authorities.
They insisted that cheese production must be carried out in licensed, fully hygienic facilities, which rules out the bottom of a lake.
"We understand Mr Boivin's goal and we're open to innovation," Normand Giguere, a Quebec provincial food scientist told Canada's Globe and Mail newspaper.
"But he has to respect Canadian regulations. This is a first."
The underwater search for the cheese was inspired by the need to test whether the inhospitable conditions are actually helpful to healthy cheese consumption.
Yet after three dives, there is so far no cheese to be seen.
"We know where the treasure is," Mr Boivin said, "but it's tougher than we thought to find it."