About swimming

Swimming extracts consumes about four times more energy than running for the same distance. In part it's It is partly because of the water resistance which, as opposed to the air resistance, substantially affects the result. Contestants of Competitive swimmers swimming even shave their hair in order to slow  reduce down the resistance. A wet suit raises the streamlining and helps to increase the speed.
The Speed is provided first of all with motions of hands. Swimmer gain speed through the effort of hand and arm motions. The legs play a less important role. The push with legs in and crawl on the chest is necessary only for to support for streamlining and not for and not forward motion. , but Swimming using only with the hands is tiresome because the legs start pulling down and reducing the swimmer's speed.