In this paper, we report a new electromagnetically-driven two-axis water-immersible scanning mirror with single inductor coil actuator. By making the resonance frequencies significantly different, the scanning motion of the two axes can be decoupled due to the dynamic structural filtering effect. For verification, a prototype micro scanning mirror was designed, fabricated and tested. The resonance frequencies of the fast and slow axes in air and water were determined to be 720/72 Hz and 690/55 Hz, respectively. The optical tilting angle of both fast and slow axes at the resonance frequencies was characterized, which shows good linearity with the amplitude of the driving current. With both axes driven simultaneously at frequencies close to their resonance, stable and repeatable 2D raster scanning was successfully achieved in both air and water, respectively. 2D B-mode ultrasound microscopy was also demonstrated by using this micro scanning mirror.