A pure-water inverted-L antenna with frequency reconfigurability is proposed in this letter. The radiation from the cutoff region of high-permittivity dielectric waveguide is here utilized in the proposed water antenna to realize the similar performance of a metal inverted-L antenna. According to the operational principle, the working frequency of proposed water antenna is mainly determined by the cross section of water rod rather than its length. It is found that a wide tuning range from 1.1 to 2.2 GHz can be achieved when the radius of cross section is changed from 2.5 to 5 mm. Two states with three-dimensional printed transparent double-layer resin container are selected to implement the frequency reconfigurability. By controlling the filling status of water, i.e., only occupying inner layer (state 1) or the whole container (state 2), the radius of water rod is altered. The operational frequency band of fabricated water antenna can be tuned from 1.41-2.04 GHz (state 1) to 1.07-1.33 GHz (state 2). The proposed antenna is intrinsically different from those conventional reconfigurable water wire antennas where length is usually tuned to attain frequency agility. Both wide frequency tuning range and stable broadside radiation are here achieved.