Patrick Williamson, 37, was stunned when his pup dropped her ball and sprinted over to retrieve the 5oz “rock”.
Fisherman Paul quickly realised it was ambergris - a valuable chunk of vomit produced in the intestines of sperm whales.
Whales are usually able to regurgitate problem foods but if they can’t they produce a waxy substance to protect their intestinal tract.
The whale will expel the valuable ambergris, which will float in the sea until it washes up on the shore – ready to be found by a lucky treasure hunter.
In the past, large lumps of the substance have sold for millions, motivating Paul to get his new discovery tested.