I disembarked at Yfor Bay well after dark, met by the swish and suck of great water. Nowhere else in the world, I had read, did the tide recede as far as at Yfor Bay, exposing vast, muddy flats, derelict tangles of kelp, mussels squirting gently in the barren expanse. And nowhere else did the tide return so swiftly, kissing the upper shore-grass in the space of a quarter-hour.