Over nearly five decades, David Christopher Gadsby pioneered biophysical research that advanced our mechanistic understanding of ion-transporting proteins in biological membranes. His passion for hands-on do-it-yourself electrophysiology, his depth of analytical rigor, and his idiosyncratic scientific aesthetic expanded the edge of discovery in two areas: the electrical character of the Na + pump, and the molecular workings of ‘cystic fibrosis transmembrane regulator’ (CFTR), the chloride ion channel whose mutations cause cystic fibrosis. His approach was flavoured by an appreciation for common underlying features between these ostensibly distinct types of membrane-transport systems. While David's focus was first on the basic molecular biophysics of a problem, he was always attuned to implications of his discoveries for human health. Based in New York at The Rockefeller University throughout his independent scientific career, and at the Marine Biological Laboratory in Woods Hole, Massachusetts, as a squid-season research-scientist, he was proficient in wrestling with problems spanning a wide swath of membrane biology: from determinants of the cardiac electrical waveform, to microsecond-timescale ionic currents in squid axons, to details of structure–mechanism relations in membrane pump and ion-channel proteins. He wore his eminence lightly and never distanced himself from the laboratory, where he often performed experiments with his own hands right up to his retirement. His reserved scientific personality, which demanded equally from his colleagues and himself immaculate data, unclouded logic, and substantive pertinence to the issues at hand, contrasted with his palpable joy in a good experiment and in his sea-loving life outside the lab.