When they smelled rotting fish, Overton, Lancashire residents Gary and Angela Williams were walking along Middleton Sands beach close to Morecambe Bay.
The couple covered the large lump in a scarf and brought it home after reading about the highly sought-after substance in a newspaper.
Gary, 48, afterwards put the lump on his fishing scales and determined it weighed 1.57kg, which is little over half the size of a lump found several years ago near Morecambe.
Gary and Angela, a 49-year-old nurse, are currently in discussions with prospective purchasers regarding the lump that was recently discovered. The stone is somewhat smaller than a rugby ball.
Ambergris, which is made from the hardened intestinal sludge of a sperm whale, is known as “floating gold” because of its scarcity and high worth to perfume producers.
It becomes a smooth, grey lump of compact rock after prolonged exposure to the sun and saline water. Engineer Gary called the discovery he and his wife made “a bit of a shock.”
“Though it smells awfully nasty. It has a very distinct smell that is similar to a cross between manure from a farm and squid. “It has the texture of a really hard rubber ball. It has a waxy, candle-like feel.
“Wax sticks to your fingers when you contact it.” He added: “If it is valuable, it will go a long way toward helping us purchase a static caravan. A dream come true, that is.” When Gary and Angela go for walks, they frequently search the beach for interesting objects.