This work proposes an energy harvester that captures the mechanical energy caused by water flow and converts into an electrical energy through the piezoelectric effect. A flexible piezo-film has been used as a transducer in the energy harvesting system and the kinetic energy of the water flow is produced by using the vortex induced vibration technique. When placing in water way the transducer is fluctuating in the vortex of the fluid flow, producing the kinetic energy of 44 mW at a low fluid velocity of 6.8 m/s and low frequency of 0.4 Hz. This configuration generates a corresponding open-circuit voltage of 6.6 mV at a matching load of 1 MW, leading to the maximum output power of 0.18 mW. An efficiency power conversion of the harvesting system was evaluated to be about 4.4 %.  It is possible to use the proposed unit under gravitational force where there is a difference in the levels of the fluid no matter in water way or transporting parts such as petroleum pipes. However, rectifying the output voltage generated by the present micro generator is compulsory in order to feed small scale electronics and communication, for instance, wireless sensor networks. Furthermore, multiple arrays of the piezoelectric unit are also promising for delivering higher output power.