On Saturday, Mr Clark's sensitive toes earned him the title of world 'tramping' champion for the third time. He caught the largest flatfish, a 2lb 2oz flounder, in the 21st annual championships at Glen Isle Sands on the Solway estuary, beating more than 100 competitors and maintaining the Scots' dominance in this eccentric sport.
Tramping - catching flatfish with your feet - is a traditional sport in Cumbria, eastern Scotland and in parts of North America. The quarry, the flounder - a plaice-like flatfish without the red spots - lives in shallow estuaries and can swim upstream into fresh water. The fish are sometimes captured in the Thames at Richmond, more than 30 miles from the sea.
Flounders are often too lazy to swim out with the tide so, relying on their camouflage, which can change chameleon-like from sandy white to muddy black, they bury themselves in creeks and rock pools. This is when the tramper sets to work.
Walking slowly through the water with bare feet, he feels for a smooth shape, rather like treading on a jellyfish.
'You don't always tread on the middle of the fish,' Robin Tilson, runner-up last year, said. 'You have to move your foot to the middle. It wriggles a little, then stays still. You reach down into the water, feeling for the head and tail, and bring it slowly up and out of the water.'
The fish is then put into a plastic bag or, in the case of some eccentrics, into their swimming trunks. Mr Tilson, who regularly fishes at Glencaple, further down the estuary, has caught more than 100lb of flounders in a tide.
There are hazards. Fortunately, Britain's only poisonous fish, the weaver, is unheard of in the Solway Firth, but crabs, which feel like a flounder at first, betray their presence by nipping your foot. All the competitors on Saturday bore crab scars.
This year's event is a triumph for traditional methods. Over recent years, there has been a trend towards using a liester, or spear, to stab the flounders. ('This is called the world tramping championships and I don't think spearing should be allowed,' Mike Clark, from Carlaverock, said.) Last year's event and the pounds 150 top prize was won by a spearer, but this year, the feet-only men dominated.
'We try to discourage using a liester, especially by the inexperienced, because there is a chance of putting the spear through their feet,' Harry Ellis, the organiser, said.
'But there are some areas where you can't fish without a spear because of the depth. And we try not to have too many rules.'