In 1857, William Thomson (Lord Kelvin) wrote to Sir George Gabriel Stokes, “Now I think hydrodynamics is to be the root of all physical science, and is at present second to none in the beauty of its mathematics.” However, 117 years later, Sir Geoffrey Ingram Taylor had a thoughtful reminder (1974): “Though the fundamental laws of the mechanics of the simplest fluids, which possess Newtonian viscosity, are known and understood, to apply them to give a complete description of any industrially significant process is often far beyond our power.”

The ultimate requirement for the understanding and quantification of the ocean--structure interaction is the understanding of the physics of turbulence, separation, and computational fluid dynamics. This is particularly true for the extraction of oil and gas. Computers (virtual simulations) and experiments (i.e., what can be calculated and what can be measured) have and will continue to have unsurpassable limitations. Even if one were able to calculate a given fluid--structure interaction, with sufficient time and resources, one will not be able to cover the entire parameter space. Thus, approximations, experiments, experience, successes and failures, empirical equations, and virtual modeling will continue to define the limits of our power to design structures that serve the intended purposes. Experience, physical insights, computers, past regrets, and future failures will continue to define the form and the substance of ocean--structure interactions. Developing the technology and carrying out the physical processes to discover and extract oil and gas, particularly from greater depths at increased risks and cost, have become one of the major challenges facing the industrialized countries, notwithstanding the efforts to develop alternate sources of energy.