It's funny you just mentioned this because we just learned a few weeks ago in physiology about Henneman's Size Principle: that the somatic nervous system recruits smaller skeletal muscle motor units (1) followed by larger motor units as the amount of force needed increases.

That would make resistance training by rowing in water better fit than some magnetic resistance machine based on what you described. Air also has same property like any other fluid, your average big body of water has enough viscosity for this property to matter at speeds we don't need cybernetics and Tommy John's surgery to survive.

(1) A motor unit is just all the muscle fibers controlled by 1 motor neuron. With this single source of signals, all those muscle fibers respond the same way.