What's stuck in the muck at the bottom of Lough Salt in County Donegal, Ireland? It could be that 20 of Old Tom Morris' golf balls are down there.
A team of divers has begun searching one of Donegal's deepest lakes for 20 gutta percha balls that the legendary golf pioneer and four-time British Open champion is said to have knocked in there as part of an exhibition while he was designing the nearby Rosapenna Golf Course in 1891.
"We've carried out some research and spoke to local people whose parents were around when Tom Morris was here and they told us how he stood up on the hill overlooking Lough Salt and drove the balls into the lake," dive leader Gus O'Driscoll told BBC News. 
"It soon became a tradition after that for golfers on their way home from the Rosapenna to stop off and drive balls into the lake," he added. "That checks out because we've seen thousands of balls on the bottom of the lake and we have recovered some which date back to the 1940s and '50s."
Because there are so many balls at the bottom of the lake, locating Morris' models is an even more difficult task than scouring the bottom of a deep, dark lake would be otherwise. But the reward could be great.
The gutta percha balls that Morris used in his heyday sold for a shilling (about 8 cents) apiece at the time. Now, however, these "little pieces of sporting history" are worth about $25,000 each, or more than $500,000 if all 20 are found, according to the Independent newspaper in Ireland. 
"The balls we are looking for were designed by Morris himself and he used them when he won the Open four times in the 1860s," O'Driscoll told the Independent. "It would be fantastic to get one of them."
Despite the balls' potential value, however, the divers aren't looking solely to cash in. If they do manage to salvage some of the spheres, they plan to make a donation the Rosapenna Golf Club.
"There's a statue of Old Tom Morris at the entrance to the course he designed," said O'Driscoll, "and it would be lovely to give the club one of his original golf balls to put on display n the clubhouse."