Historical Introduction -- Reminiscences of MODE -- Modeling Ocean Circulation -- Contributions to Global Ocean Observations -- On Reconciling Oceanic and Atmospheric Estimates of Surface Heat Fluxes-and on Validating Greenhouse Models -- El Niño and Ocean Observations -- Reflections of an Equatorial Oceanographer -- Ocean Acoustic Tomography -- A History of Thermocline Theory -- Sextant to Satellite -- Some Advances and Retreats in the Study of Ocean Circulation since 1935 -- Towards the World Ocean Circulation Experiment and a Bit of Aftermath -- Interview with Klaus Wyrtki, 25 February 1999. Over the last five decades physical oceanography developed rapidly from a branch of fluid dynamics, with only a few observations, to a mature science with global field programs, large computer resources, and a complex theoretical framework. Today understanding of ice ages, global warming, or predictions of El Niño are to a large extent due to progress in understanding ocean physics. Therefore, it is important that the history of physical oceanography is made known so that citizens can understand the current state of climate sciences and policy makers can make informed decisions about future research. This volume contains a historical introduction by Bruce Warren and twelve historical perspectives from world-renowned physical oceanographers.