Waist-deep in the heart of a vast, 3,290-acre (1,330-hectare) mudflat, I plunge my arm into the glistening sludge, my fingers sifting through the cool, dense muck until I feel a sharp shell.
“There, see those?” says a woman in her fifties, her cheeks dusted with freckles, as she gestures to tiny breathing holes dotting the slick mud.