The Welsh word is cwrwgl. The Romans wrote about it two thousand years ago. The Hidatsa of North Dakota stretched buffalo hide over willow on the Missouri. Tibetan herders crossed glacial rivers in yak-skin versions still in use today. Marsh Arabs in southern Iraq built reed-and-bitumen variants that pre-date the pyramids. Each design responds to local materials and the temperament of local water, but the principle is universal: a craft so light it can be portaged on the shoulder, so flat-bottomed it skims through inches of water, so round that it spins like a top until the operator masters a one-handed paddling stroke that looks easier than it is. Watch a Teifi coracle fisher at work and you are watching a technique transmitted, father to son and mother to daughter, across at least sixty generations.

Martin Fowler opened the National Coracle Centre in 1991, in the old flour mill at Cenarth Falls. He had been collecting coracles for years, and the collection had outgrown every available room. The mill itself, with its surviving waterwheel and millstones, became part of the exhibit: a setting for boats that, like the building, were once everyday tools rather than curiosities. The displays now include examples from Tibet, India, Vietnam, the United States, Iraq, and a dozen British river systems. Each river developed its own coracle dialect, subtle differences in beam, in stern profile, in the type of hide or coated canvas used. Walking the floors, you trace a quiet international language of small boats.

One bamboo coracle in the collection carries a particular weight of memory. It was woven in Vietnam, and used by refugees fleeing across the South China Sea to Hong Kong in the years after 1975. The vessel was never designed for ocean voyages. Coracles are river craft, calm-water craft. What it took to put to sea in one is something the boat itself cannot quite explain. The Exeter Maritime Museum donated it to Cenarth, and it now sits in a quiet corner: a basket that crossed an ocean. Nearby hangs a North Dakota bull-boat made by the Hidatsa, its buffalo hide stitched to a willow frame, a reminder that this same humble form has carried people through equally desperate crossings on the other side of the world.

The museum does not flinch from the rougher edges of coracle history. One gallery is devoted to poaching, the centuries-old shadow economy of Welsh river fishing, displaying the nets, lamps and gaffs that local men used to take salmon at night under the moon, sometimes within sight of the bailiff. Coracles work best in pairs, two boats holding a seine net between them, drifting downstream with the current; it is a method ideally suited to either licensed fishing or quiet theft. On the Teifi, Towy and Taf rivers a small number of licensed coracle fishers still work in the traditional way, the last commercial practitioners of a craft that elsewhere survives only as sport or demonstration. Workshops at the centre teach visitors to build their own, and now and then a new coracle, made by hand in this corner of Carmarthenshire, slips into the river just as its ancestors did when Rome ruled Britain.