Abstract: A manually driven fitness device includes a main body, two floating barrels respectively mounted on both sides of the main body, a front drive mounted at the front end of the main body, a rear drive speed variation device mounted at the rear end of the main body, a power transmitting device connected with the front drive and the rear drive speed variation device, and a power output device engaged with the output end of the rear drive speed variation device. The floating barrel is a hollow object, which supports the main body to float in water with its buoyancy, while the user may exert force with one's hands and feet respectively on the front power drive and the rear drive speed variation device, and stretch arms and legs in a regular pattern so as to achieve the effects of exercise on water surface or in the water.