It all began with Markus Jochum approaching one of us (HvS) – “when you guys are doing interviews with senior scientists from oceanography and related sciences, why are you not doing Walter Munk?” Indeed, why not? Walter Munk, an icon in oceanography, had just given a wonderful talk in a symposium in honor of his 90th birthday, sweeping a grand circle from his earliest work with Chip Cox on airborne measurements of ocean surface roughness to the latest satellite data – not simply a review, but the struggle of an active scientist opening up new perspectives – as inspiring and stimulating as when one of us (KH) rst met him at the Ocean Waves Conference in Easton in 1961 (Fig. I. 1). Walter immediately agreed to share with us his recollections on the nearly seventy years of his path-breaking contributions in a sheer amazing range of topics, from ocean waves, internal waves, ocean currents, tides, tsunamis, sea level, microseisms and the rotation of the earth to ocean acoustic tomography. With “you guys” Markus was referring to HvS and the various partners HvS had 1 invited to join him in conducting a series of interviews of retired colleagues.