# How would you swim in inviscid water?

The viscosity of water creates drag on swimmer's body so its effect is to slow down the swimmer. However the viscosity seems to be essential for pushing the water backwards by the swimmer's arms and legs. Would a human be able to swim in water with much lower viscosity? What standard stroke (front crawl, breaststroke, butterfly) would work best/worst? How would a lower viscosity affect fish motion in water?

• Drag coefficient depends rather weakly on Reynolds number and hence on viscosity. So even if viscosity decreased several times (if the density remained unchanged) the drag coefficient change would be much smaller so the dynamic of swimming probably wouldn't change much. Commented Jun 11, 2013 at 15:04
• Ref Commented Jun 11, 2013 at 18:39
• Somehow related: will a propeller work in a superfluid? physics.stackexchange.com/q/311069/226902 Commented Oct 10, 2022 at 12:16

• Why should we assume that drag is dominated by viscosity while the stroke is dominated by inertia forces? The Reynolds number R is the ratio of the inertial to viscous forces, and R goes as $v l$, so a smaller object (arm) which is moving faster would have about same R as the whole body - correct? Commented Jun 11, 2013 at 19:33