Why do ducklings swim in a row? « Adafruit Industries
Physics of Swimming
It is these forces which propel a swimmer through the water.
Let's assume that there are 50 swimmers in an Olympic size pool and they swim so fast that each of them consumes 1500 kJ of energy per hour and puts that much heat into the water.
The arms and legs are drawn in close to the torso, bending at the elbows and knees.
How Do Swimmers Reduce Water Resistance? The amount of inclination is given by the angle of attack.
So answers that assume a fixed amount of work by the boiler seem to me to be at best incomplete.
But even if you work hard to minimize all these factors, you'll still typically use about four times more energy swimming a certain distance than you would would running the same length.