At swim practice last week I started thinking about how the composition of the water was affecting how fast my teammates and I were able to swim. The mechanical properties of the water--viscosity, density, surface tension, etc.-- are what determine how much force swimmers are able to generate by pushing on it and how much drag they experience moving through it. And different substances, like surfactants in the case of surface tension, are able to alter those properties. So if it's possible to change water's mechanical properties by adding different substances to it, might it also be possible to develop an "ideal water" that would make swimmers faster? My initial guess is probably not, since any reduction in drag would result in a corresponding reduction in the force a swimmer would be able to generate by moving the fluid, and vise versa. (Am I correct in assuming that?) But then again, maybe there is some "perfect" set of properties that would strike an ideal balance between reducing drag and maximizing power?